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Articles from 1998 In October


Feeding AI Boars

Research indicates that top-quality rations will lead to improved libido, sperm production in boars.

When almost all boars were used in natural service breeding programs, most pork producers followed standard industry logic when it came to boar nutrition: feed them the gestation sow diet and that will be good enough.

"If semen quantity of a boar in natural service drops from 90 billion cells per ejaculate to 50 billion cells, this is still adequate to get the sow bred," observes Mark Wilson, swine nutritionist with United Feeds of Gridley, IL

A Different Time That drop in semen production becomes unacceptable in today's world of boar studs and mating by artificial insemination (AI), where each dose of semen has financial value.

Wilson says while much of the research on boar nutrition has been inconclusive, some is starting to show that feeding boars better probably pays off.

Following are the key areas of importance to top stud performance and what data shows:

Libido: A few trials showed that libido was not influenced by nutrition, including that ad lib-fed boars didn't increase semen production over moderate-fed boars.

Wilson reported that one confounding factor is that not all genotypes respond the same. Therefore, caution should be used when comparing feeding requirements of traditional and current lean genotypes.

He reported on a study of two genetic lines of Pig Improvement Company boars. Each line had two feeding regimens: one group that was limit fed and one that was fed at a high level of nutrition. The line of boars that showed significant response to higher feeding levels also gained the most body weight. The line which did not see a response showed no weight gain differences regardless of low or high feeding levels.

In more recent trials, restricting protein intake (.31% lysine) reduced boar libido, which was measured by increased time for mounting and start of ejaculation and shortened length of ejaculation time, says Wilson.

Also, he warns, producers may want to rethink scrimping on heat check boar rations. Those cheaper rations may harm libido, and in turn, reduce their ability to detect females in heat.

Overall, most producers feed boars properly, believes Wilson. But these days of low returns they might be thinking about cutting corners. He says to rethink that idea. Higher levels of protein may add $2-3/head, but that still works out to pennies per dose of semen.

"High protein diets tend to produce boars that create higher levels of estrogen in the bloodstream and those boars have been shown to mount quicker and were much quicker to collect," he says.

Sperm production: In a trial done in a cold climate, boars were given from 18 grams to 31 grams of lysine in their diet. The high-energy-fed boars were given 12 lb. of feed, the medium-energy group 8.5 lb. and the low-lysine group got 4.5 lb. of feed a day, reports Wilson. Using the same collection frequencies for the three groups, there were no differences in weekly sperm production out to six weeks. But when the study was extended out to 9 to 12 weeks, there were major differences in sperm output in favor of the high-energy group.

In a related trial done at United Feeds, all the boars responded positively in sperm production when lysine levels were increased from 14 grams to 18 grams per day, he says.

According to Wilson, using the high-protein diet from the previous United Feeds trial, researchers added a top-dress product containing some fiber. The result was an increase in sperm production in just two weeks. He says the top-dress changed the formulation of the ration such that the extra energy produced a change in hormonal expression of those boars and an increase in libido. "Boars were mounting the dummy much faster and we were getting longer collection times."

He theorizes that the boars were probably already producing the sperm. "By top-dressing the ration, we just got them to produce a better collection."

Daily energy requirements for adult working boars are listed in Table 1. Wilson says you need to feed boars liberally. His data shows boars gaining weight produce the greatest amount of sperm. Don't scrimp on boar nutrition as they get older. Boars need to maintain body condition without getting too fat.

Average crude protein for boars should range 14-16%. Lysine should range .55%-1.1%. Energy levels depend on the grain source but run from upper 22 Mcal/kg to the lower 3 Mcal/kg. Fiber content should be about 4.5% of the diet.

Wilson says most boar studs use the following micro-ingredient levels: calcium, .9%; phosphorous, .8% and zinc, 100 ppm.

Survival Tactics In A Down Market

1 Buy Feed Ingredients Now Corn and soybean meal are at unusually low prices right now. In fact, these products only get this low 10% of the time, according to Ron Plain, ag economist at the University of Missouri. So lock in, buy ahead and store your feed now.

"Prices aren't likely to get much lower," he adds. "And something like the weather could change things and prices will get a lot higher."

Jerry Shurson, University of Minnesota nutritionist, adds that shopping around for the best prices will pay, too. He suggests spending time studying the markets for the most expensive nutrients in the diet: energy, protein and phosphorus.

"If you can cover those three nutrients you have come a long way toward minimizing your diet cost," he explains.

2 Don't Overfeed While feed is cheap, it still represents two-thirds of production costs. Plain says producers should still work hard to cut feed costs.

One suggestion is to pull hogs off feed 10-12 hours before trucking them to the slaughter plant. Plain says this will save a little feed without hogs suffering any loss.

In addition, resist the urge to feed the hogs to heavier weights. This time of year, hogs put on weight faster. Plain says producers can easily end up with hogs weighing 280-290 lb. Then they may face discounts and miserable feed conversion. "As cheap as hogs are, there is no need to feed them too long," he says.

Feed costs can also be cut by fine-tuning diets. "The mindset for many producers is that low hog prices mean it's time to get serious about fine-tuning feed programs," reports Shurson. "The reality is, producers should always be fine-tuning feeding programs, regardless of hog prices."

Focus on the grow-finish phase first where the most feed tonnage is used. Shurson suggests working with independent nutritionists to customize diets specific to production conditions. Separate-sex feeding, multiple-phase feeding, feed budgeting, and changing diets at the right time, also help minimize overfeeding.

Make sure all non-nutritive additives, such as growth promotants, are paying their way. "If there are no performance or health benefits, those additives do nothing more than raise diet cost," Shurson says.

Adjust feeders regularly, at least three times/week. "You should be doing everything you can to minimize feed wastage," Shurson adds.

3 Check Production Figures For Trouble A check of your hog operation's production records could uncover problems robbing you of profits. Tom Baas of Iowa State University offers a quick list of production figures you can check your own figures against.

To be profitable, Baas says you must be above average in most of these production areas. A single weakness or strength seldom determines profitability.

These benchmark numbers are suggested figures only. If yours are considerably different, dig into why and work to improve your profitability. Here are some suggested benchmarks:

2.2+ litters farrowed/breeding female/year for handmating or confinement systems is a fair target, according to Baas. Penmating systems should look for 2.0 litters/breeding female/year.

20+ weaned pigs/breeding female/year should be the goal for most herds.

80% farrowing rate on an annual basis is a good target. Baas notes this rate will vary throughout the year.

190 days to market is a realistic goal for the average of all pigs, Baas says.

Whole herd feed efficiency should be averaging 3.3 while the grow-finish in confinement should be 3.2 or less and nursery 2.0 or less.

Feed disappearance in the grow-finish units should run 4.75 lb./head/day.

4 Tighten UP Marketing Watch market weights. "It's easy to get into the habit of trying to hold hogs until the market price looks better," reports Palmer Holden, Iowa State University swine specialist. "But if your pigs are gaining 2 lb. or more/day, in 10 days they are going to be 20 lb. heavier and they may gettoo heavy and too fat." Heavyweight pigs often mean poor feed efficiency.

Plus , hogs with too much backfat and too heavy will be docked in price by the packer, Holden adds.

Weigh your hogs and group them accordingly to reduce sort loss, advocates Plain. "It takes extra time and effort, something you should do all the time. But in these times of low prices, you really need to do it."

Plain also suggests shopping around for the best market price. "It may be quick and easy to take them to the local buying plant, but call around and get bids," he says. Producers need to work to get the best price possible for their hogs.

5 Talk To Your Lender If ever there was a time to keep your lender informed, it is now. Many producers face cash flow binds with the continued low hog prices. They should not hesitate one second to keep their lender informed, reports Steve Stanton, Farm Credit Services of the Midlands, Perry, IA.

Although many producers will not need to make changes, some will, he adds. One possibility is balancing debt load to meet their cash flow. Other options include reducing debt where possible and taking advantage of flexible loan terms.

It is also very important to work with a lender who understands the hog industry. Stanton says the hog market cycles and these low hog prices will pass. "It is important not to panic," he stresses.

No lender for a pork producer should be surprised by low hog prices. Stanton says a key thing lenders look at before making a loan is a producer's ability to withstand low prices.

What he wants to see from borrowers is a commitment to hog production and a commitment to being a low-cost producer. If prices continue to stay low, producers will really need to look over their operation for inefficiencies. And they must be willing to make the necessary changes to stay in the business for the long term.

6 Streamline Breeding Herd Producers should tighten up their breeding herd to keep from feeding and housing poor-producing animals, according to Todd See, North Carolina State University extension swine specialist. If you don't, poor performers will only add to your costs.

See suggests promptly removing sows with high, non-productive sow days. Cull boars not producing pigs with carcass premiums. If you use artificial insemination, sell boars with consistently low sperm volumes.

"Make sure the boar-to-sow ratio is where you want it to be," he says. He suggests 15-20 sows/boar for natural mating. Sow numbers per boar go up with AI.

7 Lower Sow Replacement Rates Producers might want to lower their replacement herd rates right now, See says. But don't lower it too much so that the herd becomes old.

"You don't want to stop turning over the sow herd with a replacement rate of zero," he says. Then the sow herd will be too old in the future and production problems will result.

If a farm is at 50% replacements, for example, he suggests moving to a 30% replacement rate.

Resist the urge to pull replacement gilts from finishing animals. "Don't go to the finishing floor to pick up gilts, which is what we see happen in situations like this," he emphasizes. Stay with your current replacement lines, or your breeding program will suffer, he cautions.

Quality Lean Growth Modeling Project

Pork producers have accepted the ambitious goal of making pork the "Meat of Choice." Two factors will determine their success:

More pork must be raised more efficiently in the U.S. so pork prices are competitive.

The quality of pork produced must be improved for increased consumer and processor acceptance for domestic and international consumers alike.

The results of the National Pork Producers Council (NPPC) National Genetic Evaluation Program (NGEP), reported in 1995, showed a large variance in efficiency and quality of lean produced. That same year, a Consumer Preference Study (CPS) indicated U.S. consumers can discriminate among quality (juiciness and tenderness) levels of pork. Unfortunately, the NGEP showed the most efficient animals to produce did not always result in the products that consumers preferred.

In an effort to improve production efficiency and product quality, the Quality Lean Growth Modeling (QLGM) project was funded by the National Pork Board and began in 1996.

Lean growth models are computer programs that predict growing pig performance. There are several in use by feed companies and several more in university research laboratories.

Generally, pig growth and fat deposition rates have been researched to market weights at 250 lb. However, packer buying programs are encouraging marketing at heavier weights, even past 300 lb. There is little information about feed intake, conversion, or gain on modern pigs from 250-330 lb.

Recognizing this void, the 1996 Pork Forum Delegate Body passed resolutions to research the economics of heavyweight market pig production.

Through the use of new, electronic feeding equipment in the QLGM project, more accurate daily gain and feed intake information can be captured on an individual pig basis. Also, meat quality parameters have been avoided by modelers because data was lacking and it is expensive to collect. This challenge, too, is addressed in the QLGM project.

The economics of changing diets as pigs are finished to heavier weights was also evaluated in the QLGM project. Four nutritional programs (four diets per program) were fed - all with constant energy, mineral and vitamin levels within respective weight ranges - but diets within each program differed by assigned lysine levels. Changes in growth, carcass composition and quality of loins, hams and bellies due to nutritional program differences are evaluated in the QLGM project.

The highest lysine levels (diet 1) should provide excess protein for all pigs. Likewise, the lowest lysine levels (diet 4) are below National Research Council (NRC) recommendations and should restrict most pigs (see Table 7, page 24).

The six genetic lines used in the QLGM project were selected for their diversity with the intent of representing a cross-section of genetic types in the pork industry. This program was not designed to compare genetic lines, but rather to analyze the response of different genetic types to different nutritional programs and off-test weights. Classification procedures are reviewed below.

The variation in pigs provided by six genetic types also facilitated data collection which will allow Fat-Free Lean Index (FFLI) equations to be updated. The packing plant processing the QLGM pigs installed a Fat-O-Meater and an ultrasound system along with a last rib backfat thickness measure. Every carcass was measured with all three systems. Several on-line pork quality measures were also collected.

Nearly half of the carcasses (698) were broken down into primal and subprimal cuts, fat and bone. These (one-half) carcasses were then ground and samples sent to a laboratory to determine chemical lean content. This is the largest current database on U.S. slaughter hog composition. New FFLI equations will be developed for better producer information.

Loin samples from each pig were evaluated fresh for color, pH, drip loss and intramuscular fat content. Chops were cooked at 70 C (158 F) and tenderness, juiciness and cooking loss were measured.

One ham from each carcass was separated into three muscle groups, fat and bone. Each fresh muscle group was evaluated for color, pH and intramuscular fat. Muscle groups were processed into ham, and cooking yields, sliceability, and sensory data were recorded.

One belly from each carcass was sent to a laboratory for processing into retail or foodservice bacon. Shatter loss, processing yield, lean content and sensory data were collected. This is the largest bacon processing trial on U.S. hogs.

Loin samples resulting from this project were used for another Consumer Preference Study since genetics, age, pig nutrition, health and management has been controlled. The consumer studies were conducted during October 1997.

This program spanned three years (1996-1998) because a portion of each of the three groups of about 550 each were grown to 330 lb. The first group of pigs entered SEW nurseries on March 5, 1996 and the last went to slaughter in November 1997.

Program Design The NPPC Genetic Programs Committee wanted variation in genetic types of pigs so that more information could be provided to producers. All seedstock suppliers were offered a chance to enter 300 terminal-cross market pigs in this trial. No ordered genetic sampling of these populations was done so these QLGM results do not represent a genetic evaluation.

A full range of performance for growth, carcass composition, and meat quality was desired for this project. Previous results reported from the National Genetic Evaluation Program (NGEP) provided good direction but several unknown genetic types were also offered. One (DeKalb Swine Breeders) was chosen for this QLGM project.

The QLGM pre-trial classification parameters used by the NPPC genetics committee are shown in Table 1. The committee relied on NGEP results for Berkshire, Duroc, Hampshire, Newsham Hybrids and Danbred to classify genetic type of entries. DeKalb entries were unknown except for supplier information that indicated good growth, good lean and unknown meat quality. Table 2 shows the pre-test classification of each genetic type based on the NGEP results.

Actual QLGM project results of a genetic type may differ from these due to sampling of pigs, but differences should be consistent between classes.

The actual QLGM project results (Table 3) were used to build Tables 4 and 5 to provide a guide for producers to use in classifying their genetic lines and matching them to the QLGM results. Those post-test classifications appear throughout this publication to provide an easy reference. More accurate lean growth curves, such as those outlined by de Lange in Table 2, page 10, will help producers more precisely classify their market hogs.

The final results of the QLGM project show general agreement with the pre-test classifications and reveal success in measuring large variation for all traits.

The QLGM project evaluated 1,590 pigs in three test groups. The genetic types included high, medium or low classifications for backfat thickness, growth, feed intake and meat quality. Crossbred pigs representing Berkshire, Duroc, Danbred, Newsham Hybrids, Hampshire and DeKalb genetics were evaluated. All program pigs were tested for HAL genotype. And, because this test was not designed for genetic comparison, each genetic type was randomly assigned a letter, A through F, to ensure anonymity.

Other sampling and procedural parameters included:

Three pigs per litter (barrows and gilts) were entered whenever possible (see Table 5). The test pigs were assigned to slaughter weights of 250 lb., 290 lb., and 330 lb. when placed in the SEW nurseries. However, due to slow growth and the protocol of selling the last pig in a pen, a few pigs did not reach their 330 lb. assigned weight (Table 6). Sex of pig was balanced among the three slaughter weights. Sampling of genetic populations was determined by the NPPC Genetic Programs Committee.

All pigs were commingled in SEW nurseries at between 8 and 19 days of age. SEW programs of NGEP were followed. That protocol included Ivomec treatment on day 1, Naxcel on days 1 and 2, Mecadox in the feed, and Denagard in the water from day 2 through 10. Pigs were penned by genetic type and size in nurseries.

Pigs were removed from the nurseries at 40 lb. and moved to a grower building.

At 80 days of age, pigs were moved to a building equipped with electronic feeding and pig weighing equipment (FIRE system) until desired market weight was achieved.

Each pig was evaluated bi- or tri-weekly for backfat depth and loin muscle area by a National Swine Improvement Federation (NSIF) certified real time ultrasound technician. This resulted in up to 10 measurements on the heaviest off-test weight pigs. Scan measurements for intramuscular loin fat or other locations of interest (ham, belly) were also recorded. These serial scan measures are used to estimate growth and lean deposition rates for each pig. The rates of backfat and loin muscle change in the Robison (page 26) article are based on the serial scan data.

The electronic feeding system monitored daily feed intake for each individual pig. Pigs were weighed at each scanning.

At slaughter, a five-rib loin section was taken from one side of the carcass. One section of three ribs was used for meat and eating quality traits evaluation and the other section of two ribs frozen for consumer preference studies (CPS). The CPS loin samples were individually vacuum sealed in plastic bags and deep frozen until needed.

A sample of half carcasses was physically separated into lean, fat and bone to provide data for refining the Fat-Free Lean Index equations.

Boneless primal cut weights were taken during carcass separation.

Ham and belly quality measures were collected and evaluated at meat laboratories.

Four nutrition programs of four diets each had constant energy, minerals and vitamins within a weight range of pigs, but offer different levels of lysine (see Table 7). Tylan was included in all diets. Lysine was supplied by corn and soybean meal in all diets. Feed was fed in ground form at smaller than 750 microns particle size. Added fat was choice white grease.

Pens of pigs were randomly assigned to a nutrition program. Feed was delivered in an electronic feeding system (FIRE) that weighs daily feed intake by means of an electronic ID in a pig eartag. All feed delivered to the FIRE system was weighed by scale cart as a check against the FIRE data.

This project was completed at the Minnesota Swine Testing Station since SEW nursery, grower building and finishing buildings were available. Air temperature and humidity, pig health and other management data were also completed for future model testing.

Presentation of Results There is a very large amount of data resulting from this project and several possible ways to do statistical analysis to answer questions.

The succeeding articles by Robison, Johnson, and McKissick have tried to be as consistent as possible in their reporting.

Understanding Lean Growth:An Overview

The commercial pork industry's number one challenge is to provide consumers with safe, wholesome food of a high and consistent quality. This food should be produced as efficiently as possible, while considering the impact on the environment, animal welfare, and the well-being of people involved with the production process.

Lean growth - that is lean meat deposition in pigs - is closely associated with the efficiency of pork production for various reasons:

First, it represents the growth of the valuable parts in the pig's body.

Second, lean growth is closely associated with body protein deposition. Body protein deposition, in turn, is the single most important factor that determines dietary amino acid requirements and is one of the main factors determining the dietary requirements for energy in grower-finisher pigs. Energy and protein account for over 85% of the ingredient costs in practical pig diets. Feeding costs are the single most important cost factors in commercial pork production.

Third, lean growth is much more efficient than the accretion of body fat. It requires approximately four times the amount of energy to grow one pound of fat tissue as compared to the energy required to grow one pound of lean tissue.

And fourth, there is considerable variation in lean growth rates between different groups of pigs. For example, the anticipated growth performance and carcass quality of pigs with high, medium or unimproved lean growth rates are presented in Table 1. These performance levels are at energy intake levels considered typical for commercial pig units.

These data indicate that under typical market conditions, an increase in lean growth rate of 5% will translate to at least an additional $1 profit/pig. Therefore, it is important to understand what contributes to differences in lean growth rates between groups of pigs and hopefully to identify the means to increase lean growth rates and the efficiency of pork production.

Calculating Lean Growth Rates Lean growth rates can be calculated from carcass weight at slaughter, the estimated lean content in the carcass, an assumed lean content in a pig's body at the initial weight, and the amount of time required to grow from initial weight to slaughter weight.

Table 2 reviews the steps used to estimate the lean content in pig carcasses and to calculate lean growth rates in different groups of grower-finisher pigs. These calculations were taken from a comprehensive publication of the National Pork Producers Council (NPPC).

Unfortunately, the definition of lean and methods used to quantify the amount of lean that is present in pig carcasses may vary between and among packing plants, pig breeding organizations and research institutions. In particular, the amount of lean present in the belly may be estimated in different ways. Likewise, miscellaneous muscles (in addition to those from the main lean cuts) may or may not be included in total lean. Or, the amount of lean may be standardized to different fat contents.

To complicate matters further, there is a range of carcass measurements used to predict the lean content in the carcass. Relationships between carcass measurements and actual carcass lean contents differ between different genotypes or genetic lines.

Obviously, there is a need to clearly identify how lean is defined and quantified when carcass lean contents and lean growth rates are determined. In addition, we should continue to strive towards a clearly defined, common, unbiased and practical definition and a means to measure lean content in pig carcasses. The Quality Lean Growth Modeling project, coordinated by the NPPC, demonstrates some important leadership in this area.

Lean Growth Curves In addition to average lean growth rates, the change in lean growth rate with increases in body weight should be considered. In particular, for the development of multiple-phase feeding programs, these lean growth curves should be established. Furthermore, for determining the optimum slaughter weight, the change in lean growth rate around the time of slaughter should be estimated, as it determines the rate and cost of producing marginal increments in carcass lean content.

There are three segments to a typical lean growth curve (Figure 1 on page 14). During the early stages of growth, generally up to about 110 lb. body weight, the daily lean growth rate increases.

Between 110 and 176 lb. body weight, the daily lean growth rate is relatively constant.

At approximately 176 lb. body weight, the daily lean growth rate starts to decline towards zero when the pig's mature lean body weight has been reached.

Research conducted at Purdue University, plus observations on commercial pig units, indicates there is considerable variation in the shape of this lean growth curve between different groups of pigs. These variations are particularly noteworthy in pigs over 220 lb. body weight. Results from the NPPC Quality Lean Growth Modeling project will provide important information about lean growth curves in different types of pigs exposed to varying nutritional regimens.

Pig Growth Models Sound information about lean growth curves is vital for the on-farm use of pig growth models. The adjoining sidebar on page 15 reviews the type of information you will need to drive various growth models.

Pig growth models are computer programs that integrate our current knowledge of nutrient utilization for growth and of animal environmental interactions into one system. Lean growth - body protein and body fat deposition - are important drivers of these models because they are increasingly used to finetune feeding and management strategies on individual pig units.

When well-tested models are used properly, they can be valuable tools to improve profitability. In particular, these models can be used to identify what factors determine lean growth at the various stages of growth and thus how lean growth can be manipulated.

What Affects Lean Growth Rates 1. Pig genotype: The pig's upper limit to lean growth or lean growth potential, is determined by genotype, which also includes their sex.

The information contained within the pigs' genes determines lean growth potential. The pigs' lean growth potential and the lean growth potential curves are the results of complex interactions between many different genes. It is thus unlikely that a gene or gene probe will be identified in the near future that will allow us to quickly and reliably identify pigs with high lean growth potentials. However, lean growth potential has a medium to high heritability, so conventional and intensive genetic selection will result in substantial improvements in lean growth potentials of pigs. The practice of crossbreeding is likely to result in only modest improvements in lean growth potentials.

Lean growth potentials are higher in gilts than in barrows. During the grower-finisher phase, the difference in lean growth potential between gilts and barrows is approximately 5%, but ranges from 2% to 15%. This difference appears to vary with genotype.

The difference in lean growth potential appears small up to about 66 lb. body weight, then increases as pigs get heavier. A decline in lean growth potential with increasing body weight begins at a lower body weight in barrows than in gilts. These differences in lean growth potentials should be considered when developing split-sex feeding programs and for determining the optimum slaughter weights for gilts vs. barrows.

Carrying the point one step further, lean growth potentials are higher in boars than in gilts and barrows. Although eliminating castration represents an important means to improve the efficiency of pork production, concern about boar taint and the associated effects on meat quality remains a challenge.

It is important to note that estimates of lean growth potential are usually derived from observed growth rates and carcass characteristics of pigs managed under supposedly ideal, unlimited conditions. However, whether observed lean growth rates match lean growth potential usually remains unconfirmed. To do so would require recording whether a change in nutrient intake or a change of environment altered the oberved lean growth rate. In particular, at lower body weights and in modern pig genotypes, observed lean growth rates are often determined by energy intake and not by lean growth potentials. As mentioned earlier, in order to find a means to improve lean growth rates, it is important to identify factors that determine lean growth at the various stages of growth.

2. Nutrient and energy intake - Sub-optimal intakes of essential nutrients and energy will limit pigs from expressing their lean growth potential. For this reason, practical pig diets are generally over-fortified with the relatively inexpensive nutrients, vitamins and minerals. Furthermore, close attention should be paid to dietary levels of energy, lysine, and the other essential amino acids and to daily feed intakes when managing grower-finisher pigs.

Intake of lysine and other essential amino acids: In the latest version of "Nutrient Requirements of Swine" from the National Research Council (NRC), it is clearly stated that pigs with higher lean growth rates require higher daily intakes of lysine and other essential amino acids. In this publication, it is suggested that pigs require 4.7 g/day of digestible lysine per 100 g/day of fat-free lean gain. In addition, pigs require .036 g/day digestible lysine per 2.2 lb. of metabolic body weight for various body maintenance functions. This indicates that lean growth rate is the main determinant of daily lysine requirements and that failure to meet required lysine intake levels will lower observed lean growth rates and the efficiencies associated with it.

The requirements for other essential amino acids can be derived from lysine requirements based on optimum amino acid to lysine ratios for lean growth and maintenance.

Energy intake: The generalized relationship between energy intake and lean growth is represented in Figure 2. Over a given body weight range and assuming that no other nutrients limit lean growth, there is generally a linear relationship between energy intake and lean growth. Lean growth increases until the animal's energy intake is just sufficient to achieve its lean growth potential. Beyond that point, any further increase in energy intake will not increase lean growth. Rather, the additional energy intake will simply increase the rate of body fat deposition, resulting in a fatter carcass and poorer feed-to-gain ratios (feed conversion). The point at which lean growth is just maximized indicates the level of energy intake at which the efficiency of lean growth is maximized.

Figure 3 shows the considerable variation between genotypes in the relationship between energy intake and lean growth. In fact, in some of today's modern genetic lines, energy intake is insufficient to reach the animal's lean growth potential even when these pigs are fed ad libitum and when they reach 198 to 220 lb. body weight (see LW x LD(A) boars and hybrid gilts in Figure 3).

Yet, in other genotypes, high lean growth potential can be reached at relatively low levels of energy intake (see LW x PP boars in Figure 3).

The differences can largely be attributed to variation in the increase in lean growth per unit increase in energy intake. This is the slope of the linear relationship between energy intake and lean growth in Figures 2 and 3. This variation in the slope is largely due to differing amounts of essential body lipid that different pig genotypes need to deposit, even when energy intake limits lean growth.

Body weight effects, previous nutrition, and differences in maintenance energy requirements between different genotypes further complicate the relationship between energy intake and lean growth. In particular, the effects of body weight should be considered.

The slopes in Figures 2 and 3 decline with increasing body weight. This implies that pigs get fatter when they grow heavier, even when energy intake limits lean growth, and that increasing amounts of energy intake over maintenance are required to maintain a lean growth constant with increases in body weight.

Under commercial conditions, energy intake over maintenance often does not increase in pigs over about 132 lb. body weight. Observed increases in feed intake with increasing body weight are often barely sufficient to satisfy the pigs' increasing energy requirements for maintenance. As a result, observed declines in lean growth rates as pigs reach market weight may be a reflection of a lack of energy intake over maintenance, and not of declines in lean growth potential with increasing body weight (Figure 1).

The discussion about the relationships between energy intake, lean growth and body weight have various implications.

First, these relationships are important for determining the optimum energy intake level over the various body weight ranges.

Second, it supports the need to better characterize these relationships for modern pig genotypes.

Third, in modern pig genotypes, energy intake, and not the animals lean growth potential, is likely to determine lean growth up to 220 lb. body weight or even higher. This implies that close attention should be paid to feed intake levels in finishing pigs, including a means to increase these levels.

And fourth, we have to be very careful with the interpretation of lean growth curves that have been established at one level of energy intake. Changes in energy intake levels will affect lean growth rates at lower body weights but may, or may not, affect lean growth rate at higher body weights. The latter is important as there is considerable variation in feed and energy intake levels among pig units, even for the same genotypes managed on different units.

3. Environmental stresses - Over the last few years, we have become more aware of the negative effects environmental stresses can have on lean growth rates. Crowding of pigs, excessive environmental temperatures, and disease-causing organisms can prevent pigs from expressing their full, genetic performance potential. Researchers have reported that exposure to disease-causing organisms can depress lean growth rates by as much as 30%.

Environmental stresses will affect the animals' expression of lean growth potential, as well as the relationship between energy intake and lean growth. The challenge to producers is to minimize pigs' exposure to environmental stresses. The challenge to researchers is to improve our understanding of the mechanisms whereby these stresses affect animal performance. This should allow producers to quantify what extent pig performance potentials are depressed and to manipulate the pigs' response to environmental stresses.

Factors Affecting Meat Quality As mentioned earlier, we have to consider the quality of pork that we produce.

Pork quality can be evaluated in a variety of objective and subjective ways, although the ultimate quality measure is acceptance by the consumer.

Studies supported by NPPC clearly illustrate that there is considerable variation in consumer acceptance of pork from different groups of pigs, and that there is no clear relationship between lean growth rates and the various aspects of meat quality.

Furthermore, nutritional and management strategies around the time of slaughter can have important effects on pork quality. Whenever alternative strategies to manipulate lean growth rates and lean growth curves are evaluated, the impact of these strategies on pork quality should thus be considered.

Conclusions In growing-finishing pigs, lean growth rate is closely associated with the efficiency of pork production. Plus, lean growth curves should be considered when determining optimum feeding and management strategies for individual pig units.

A proper interpretation of lean growth curves is important as different factors (genotype, sex, amino acid or energy intake, and environmental stresses) may affect lean growth at different stages of growth. The latter is important for the manipulation of lean growth rates and lean growth curves.

T here is a clear need to establish potential lean growth curves for the main pig genotypes and to identify how the expression of lean growth potentials can be maximized. When other strategies to manipulate lean growth rates and curves are evaluated, the impact of these strategies on quality should also be considered.

The benefits of using well-tested, computerized, pig growth models to fine-tune feeding programs for individual grower-finisher pig units can be substantial. For an effective on-farm application of these models, it is important that accurate model inputs are obtained and that good communication is established between the person operating the model and the manager of the pig unit where the model is applied.

The main steps involved in an effective on-farm application of pig growth models are:

1 Establish a lean growth curve. The importance of this is discussed in the "overview" article. Lean growth curves can be established using three different methods:

Calculate the average lean growth rate over the entire grower-finisher phase from initial and final body weight, carcass data, and the number of days required to grow pigs from initial to the final body weight (see Table 2 on page 10). Observations should be obtained from at least 40 representative pigs.* Use this average lean growth rate and the shape of a typical lean growth curve to establish the actual lean growth curve. This is the easiest method and is described in detail by NRC (1998). This is also the least preferred method as it ignores differences in the shape of lean growth curves between different grower-finisher pig units.

Establish a growth curve based on at least four equally spread data points that relate body weight to age. Observations should be obtained from at least 40 representative pigs per data point.* Combine this information with an actual feed intake curve (point 2, below) and run this through a well-tested pig growth model. Then adjust the lean growth curve inside the model to fit the "predicted" growth curve to the "actual" growth curve. The use of models to generate a lean growth curve is more accurate than the first method. However, it is very sensitive to assumptions about maintenance energy requirements and to the accuracy of feed intake measurements.

Directly establish a lean growth curve based on at least four equally spread data points that relate lean tissue mass in the pigs' body to age. Observations should be obtained from at least 40 representative pigs per data point.* The simplest means to estimate the lean tissue mass in the pigs' body is the use of B-mode real time ultrasound equipment. This is the preferred method. However, it requires that accurate relationships between ultrasound measurements (loineye area and backfat thickness) and the actual lean tissue mass in the pig's body are established. Unfortunately, the latter is not always the case because these relationships differ between pig genotypes and the use of incorrect relationships can lead to substantial errors in the established lean growth curve.

2 Establish a feed intake curve. Feed intake affects animal performance. Also, estimates of feed intake are required to establish the target nutrient levels in the various diets. As it is extremely difficult to accurately predict how much feed pigs consume at the various stages of growth, it is essential that feed intake is monitored routinely when pig growth models are applied.

Reasonable feed intake curves can be established when feed intake and average body weights are measured accurately over at least a two-week period, and at least at three different stages of growth that are equally spread over the growing-finisher period. Data should be obtained from at least two feeders and at least 40 pigs per body weight range.*

3 Characterize diets and feeding program. To characterize diets, establish ingredient composition, available energy and amino acid content in the ingredients, fineness of grind, additional processing, and mixing accuracy. To characterize the feeding program, establish what diets are fed over the various body weight ranges.

4 Characterize the main environmental factors known to influence animal performance. These include the effective environmental temperature, stocking density and the presence of disease-causing organisms. If lean growth and feed intake curves are established routinely, an accurate description of the environment is less critical, as these are reflected in observed performance levels.

5 Compare current, observed levels of animal performance to model predicted animal performance. This is to obtain confidence in the predictions generated by pig growth models and in suggested alterations to the current feeding or management program. These comparisons may also be used to make adjustments to model inputs, provided that clear reasons to make these adjustments are identified.

6 Identify alternative feeding and management strategies to be considered. This includes an identification of the potential ranges in nutrient contents in the various diets, formulation and pricing of various diets (to identify diets with the lowest cost/unit of nutrients), and identification of alternative feeding program.

7 Identify production objectives. Is the objective to maximize income per pig, income per pig place per year (considers income/pig as well as throughput), or maximizing the expression of performance potentials (applies when animals are selected to serve as parent stock for the next generation)? In addition, factors such as the cost of disposal of nutrients excreted with pig manure may have to be considered. Each of these objectives requires a different management strategy.

8 Evaluate alternative feeding and management strategies. Use the model to systematically evaluate alternative feeding and management strategies and to identify the optimum solution that meets the desired production objectives and other criteria set out under point 6.

9 Verify projected management and feeding performance changes. Confirm that the suggested changes to the management or feeding strategy do indeed result in the anticipated changes in animal and economic performance (i.e. continue to monitor pig performance and carcass quality).

10 Review feeding and management plan. On a regular basis, review the suggested feeding and management strategies as pig conditions, environmental conditions (changes in lean growth curves or season), or economic conditions (prices) change.

* The actual number of observations required to establish reliable growth, lean growth or feed intake curves will differ between pig units because variability in pig performance differs.

If split-sex feeding is to be applied, these observations should be made for each sex. User-friendly programs such as PorkMa$ter can be used to establish these curves from accurate measurements on representative groups of pigs.

PorkMa$ter is a computerized, performance-monitoring system for grower-finisher pigs based on feed intake and growth curves. Dept. of Animal and Poultry Science, University of Guelph. Internet website address: http://www.aps.uoguelph.ca/~porkm

Feeding For Lean In Lean Times

As the industry struggles in a down market, we must do an even better job with the small details in each operation. Many daily inputs can't be altered. But one input we can alter is feeding.

The swine nutrition industry has made great strides in feeding for a leaner carcass. The industry has also done its job evaluating feedstuffs for the relative value of diets.

Knowing what a pig needs for maximum performance, however, takes more work. As we feed closer to the pig's needs, we spend less money on nutrition/lb. of lean pork, put less into waste material, and make the pig more efficient.

To improve pig efficiency, you must tackle the two most difficult things there are to measure: feed intake and the pig's actual nutrient needs. Figuring feed intake (lb/head/day) is a simple calculation - take the amount of feed consumed in a given day divided by the number of pigs.

But getting the data for the calculation is difficult with feed delivery systems that do not measure daily usage. We usually don't know when groups of pigs run out of feed. And we are unable to accurately estimate feed left in bulk bins or feeders. Producers who want the data use weigh bars on hoppers or bulk bins to measure feed delivered. Other systems are being developed to weigh feed on the fly to help evaluate feed consumption.

The difference between feed consumption and feed disappearance needs clarification. Feed disappearance is feed consumption plus feed wastage. In most cases, we talk in terms of feed consumption when we mean feed disappearance.

In fact, I still see farms that appear to be bedding with feed. Although feed costs are fairly cheap now, they are still not that cheap. I like to see at least 50% of the feeder tray visible at any given time.

Figuring Nutrient Needs Pigs have different nutrient needs based on many factors including sex, season, environment (pen density, room temperature, facility design) and genetics. Figuring the nutrient needs of the pig at farm level is difficult. A genetic supplier may publish "nutrient requirements" but as the factors listed above change, so do the requirements.

Matching requirements with diets is an ongoing challenge. Modeling programs are available commercially that use on-farm data to get closer to actual performance than standardized industry growth curves. Some feed suppliers offer these programs. The National Research Council (NRC) has one program available that may be adapted to your unit.

The best program to date is called serial ultrasound testing. It can be used to measure a group of pigs throughout the finishing period to fix growth based on current building conditions. This data is then plotted to establish that farm's actual performance based on genetics and building type. However, information from this technique is not transferable between farms and is accurate only for that specific situation.

Case Study No. 1 In a 120-sow, farrow-to-finish operation, the sows were housed in groups. Batch farrowing occurred every 28 days. Groups were farrowed within a 7-day period to run farrowing, nursery and finishing all-in, all-out. The finishing pigs, housed outside, were fed as a mixed-sex group. Genetics were scheduled to be changed.

When we measured consumption over time, we found maximum intakes occurred from 150-220 lb. With good feeder adjustment at peak consumption, feed disappearance was 8.3 lb./pig/day. This was much greater than expected.

Once we knew intakes, we went back and adjusted protein and lysine levels down to match consumption. No limiting performance changes were noted on subsequent finisher closeouts. Although we did not impact lean on this farm, we were able to cut feed costs.

Case Study No. 2 In a weaned-pig-to-finish operation, 1,200 pigs weighing 10-11 lb. were received every eight weeks. Newly weaned pigs were housed in a power-ventilated nursery and later moved to a double-curtain-sided finisher. The unit had used closeout data to establish nutrient needs of the finishing animals. Ultrasound tests were conducted on 7% of one room of finishers.

>From the data set that was developed, the rations were changed to reflect >the growth rate of the pigs at various stages. In general, the old rations >underestimated theability of the pig to grow between 50-120 lb., and >overestimated the growth over 200 lb. Energy-to-lysine ratios published by >Kansas State were used to formulate rations.

The increased diet cost of the early rations was offset by the decreased diet costs in the latter rations where tonnage is greater. The end result was improved average daily gain, improved feed efficiency and decreased feed cost/lb. of lean gain. Since these changes, the diets have again been altered to account for the decreasing cost of energy in the corn-to-added fat ratio.

Although the data is difficult to obtain, it is valuable in both performance and cost of gain. If you have not reviewed your feed program recently, you may want to contact your nutritionist or veterinary consultant to take advantage of new information and changing feed costs.

Farmland To Report Plant Hog Prices

A new market hog price report direct from a pork packer is now available for producers to read. The report is provided from a packer and reported on the Internet website of the National Pork Producers Council (NPPC) and National Pork Board. The report was expected to begin Oct. 1. The website address is: www.nppc.org

Initially, the report will be prices received from Farmland Industries Meats Group. NPPC hopes to expand the report to prices received by other pork packers.

Farmland will provide an average price of the previous day's open market transactions. This price will include the average price paid for the purchase, the average backfat, average percent lean, and average carcass weight. The actual high price and actual low price for that previous day will also be reported.

"As a result, producers will be better able to understand the relationship between quality and price," explains Wayne Snyder, vice president of Farmland's livestock production. "We're not going to say, 'Here's the base price and you figure out the quality premiums on top.'"

Farmland's quality premium grid will also be published so producers can determine prices for any quality hog.

Criticisms of USDA's current market hog price reporting system center on that point. USDA's figures are base prices only. No premiums are included. Plus, the prices are reported on a live basis, when many producers sell on carcass weight. (USDA does plan a revision in their reports. See sidebar.)

This new report represents a first for NPPC. Never before has the organization reported market prices. NPPC President Donna Reifschneider defended this move saying, "In order to make the right marketing decisions, producers need expanded information."

She added that NPPC has been working with USDA and the pork packing industry to come up with a meaningful price reporting vehicle. "We think we've found it," Reifschneider says.

Contract Hogs Not Included Farmland's reports will involve between 8,000-10,000 hogs/day, all bought on the open market. They will not report hogs sold on contracts. Why?

"The number of different contractual arrangements in existence is almost too numerous to count," Snyder explains. "I think we can confuse the marketplace quite a bit by listing the contract price for maybe 100 head or even 100,000 head. It would mask the validity of the open market."

Prices from each of Farmland's four market locations will be reported including: Crete, NE; Denison, IA; Dubuque, IA; and Monmouth, IL.

NPPC acknowledges that many producers do not have access to the Internet. Therefore, they are encouraging farm broadcasters, newspapers and wire services to use this information.

"Congress and USDA have struggled for years to define what needs to be comprised in a mandatory price reporting system," says Al Tank, NPPC's executive vice president. Possibly, a voluntary system with packers willing to participate will offset the push for mandatory reporting.

"Having a voluntary approach should be of value to all packers," adds Reifschneider. "Some packers wouldn't want to participate (in a mandatory system)."

Mandatory Reporting Considered In fact, Congress will consider a bill calling for mandatory price reporting by packers, including hogs sold on contracts. The bill is contained in the 1999 agricultural appropriations bill.

Recently, attorney generals from 20 states endorsed the mandatory price reporting provision. Iowa Attorney General Tom Miller led the endorsements, saying farmers need open and fair markets with the current concentration in red meat production and packing.

There is no doubt among the NPPC leadership that a better price reporting system is needed, especially with the changes occurring in industry structure.

"Less and less information is available at a time when more information is absolutely essential for producers to make the right decisions," Tank says. "This is no failure of USDA. But the prices being reported probably are not reflective of true values being paid to producers."

The USDA Market News Service plans to revise their market hog price reports soon. The revisions could come as soon as this month (October), according to John Van Dyke, chief of Livestock and Grain Market News.

The biggest change being considered is a switch from prices reported on a live basis to a carcass basis. Van Dyke says they have reported some premiums and discounts in their lean value reports and will continue to do so.

"We've been gradually changing, but this is an opportunity to more accurately reflect the latest buying and selling procedures in the industry," he says. The proposed revisions are currently under pork industry review.

Delegates Endorse New Voluntary Checkoff

In mid-September, state pork producer delegates met in a special session and gave near-unanimous approval to a new voluntary checkoff program. Meeting in the nation's Capitol, state representatives were called to act on a resolution tabled during the National Pork Producers Council annual meeting in Reno last March.

Delegates had chosen not to act on the Voluntary Investment Program (VIP) at the annual meeting, noting they wanted the proposal to receive ample study and discussion at state association meetings this summer, before making a final decision. Annual meeting delegates had set an Oct. 1, 1998, deadline for action on the resolution.

The primary driving force behind the VIP proposal was the need to develop necessary funds to address a constant barrage of pressure in recent years by local, state and federal lawmakers, regulators and environmental authorities. Legislative checkoff funds (.0045% of value on all market hogs, feeder pigs and breeding stock) cannot be used to represent pork producer views in public policy issues or in legal counsel representation. The proposed VIP funds, like other non-checkoff funds generated by state and NPPC efforts, can be used for such purposes.

The special delegate session was called to meet in conjunction with NPPC's annual legislative seminar held each September and to meet the Oct. 1 deadline.

Key Points Of Voluntary Checkoff The key points in the resolution before the delegates was whether NPPC should establish a voluntary checkoff program in conjunction with the state associations:

The checkoff rate would be 5 cents per market hog or sow collected at the point of sale.

The VIP revenue would be split equally between NPPC and the states.

The Packer Processor Industry Council (PPIC) would be strongly urged to establish a similar VIP contribution at half the producer rate or 211/42 cents on all market hogs or sows and/or the processed product equivalent. All PPIC funds would go to NPPC.

Minnesota delegate Jim Quackenbush asked for confirmation that the accounting procedures could/would track where the dollars are generated, from which states.

"It seems to me that part of the need for this program is to move dollars from some of the larger states, where they are generated, to those states that have the need but can't generate the dollars," Quackenbush noted. "If we have areas of the country that do not totally support this program, will that affect their allocation when they come back to NPPC to request dollars to help with their battles?"

The "pay-to-play" question remained unanswered. Delegates were told VIP fund allocation will be assigned to an NPPC governance committee that will oversee the funds and the issues targeted. NPPC will proceed to refine those details now that the resolution received delegate endorsement.

The resolution passed pretty much unscathed except for an amendment offered by Illinois delegate Rich Brauer. He amended the resolution as follows: "The voluntary investment program will be evaluated by the NPPC voting delegates at the conclusion of the fifth year of its existence to determine if it has been successful in meeting the original goals and to determine if the program should be continued."

What amounted to a "sunset clause" on the delegates' endorsement, Brauer suggested the clause could serve as a good review point for the program and perhaps revisit whether the 50-50 split was the best allocation of funds.

The resolution passed and became a part of the final resolution passed by the delegate body.

What Next? The target, start-up date for the voluntary investment program is Jan. 1, 1999. If 100% participation is realized, an estimated $4.8 million would be collected. However, NPPC conservatively projected a 28% participation in VIP or roughly $1.4 million.

Using the 50-50 split prescribed in the resolution, $700,000 will be returned to the states, $700,000 will be retained by NPPC. Administration and collection fees will be borne by NPPC, estimated at 9%, leaving them $580,000 for program spending.

The projected VIP spending plan for the NPPC portion breaks down as follows:

40% for public awareness/education effort, including research public concerns about pork production; develop media programs to improve public understanding of modern pork production practices.

24% for trade policy/market access issues including expanding export markets while protecting well-established pork markets.

16% for environmental policy development, legal and specialist assistance to direct outcome of EPA regulations and guidelines.

12% for general state assistance including legal assistance for state and local issues, public policy education for producers and expansion of public policy efforts in Washington, DC, and state legislatures.

8% targeted for food safety issues, encouraging more pork producer input in the regulatory process, including the impact of on-farm regulatory programs.

Now that the VIP resolution has passed, NPPC will refine and implement allocation procedures through existing producer program committees and the NPPC Budget Committee. Ultimately, however, the NPPC delegate body and the organization's board of directors will guide the allocation of VIP funds.

At the state level, pork producer associations, through their delegate bodies, standing committees, and board of directors will determine how their share of the funds will be spent.

This is not an "implied consent" program as previously discussed at the annual business meeting. Rather, each pork producer will receive a consent form at the point of sale. If the producer voluntarily signs the form to participate in VIP, the packer or marketing firm will deduct a nickel per market hog or sow and send it to NPPC. And NPPC will, in turn, forward 211/42 cents/hog or sow to the producer's state association.

Without a signed VIP Consent Form, no funds will be checked off. Since the program is completely voluntary, no provisions will be made for checkoff refunds.

The current legislative checkoff remains intact. Those funds cannot be used to address public policy issues.

The next step is to develop materials to explain the VIP program to all pork producers.

NPPC staff will meet with packer representatives to outline program, establish collection and program management procedures.

Special News Section

Ag Area Law Struck Down The Iowa Supreme Court in a unanimous verdict Sept. 23 struck down the state's 16-year-old Ag Area law.

The law exempted Iowa farmers in the state's 684 designated areas from manure odor and other frivolous lawsuits provided the land was kept in agricultural production.

"The ruling could expose many hog producers to politically motivated lawsuits and hurt independent farmers who don't have the resources of larger corporations," says Norman Schmitt, president of the Iowa Pork Producers Association (IPPA).

While Iowa farmers still have nuisance protection under both House Bill 519 and Senate File 2394, which added some nuisance provisions this spring, "this ruling casts a cloud over whether or not those provisions will hold up in court," says Schmitt, a Rudd, IA, pork producer.

Schmitt believes this is the first time the Ag Area law has been tested and it is the first one in the nation to be overturned on the basis of it being unconstitutional. Most other states have some similar type of nuisance law protection, he points out.

The Ag Area law was passed in 1982 by the Iowa legislature to protect farmland. It was contested in Kossuth County in 1995, when the county board of supervisors had allowed a 960-acre tract of land to be designated a special agricultural area. The state high court agreed with neighbors who challenged the law because it denied them the right to sue.

According to the IPPA, the court ruled that giving farmers such blanket immunity from lawsuits creates easement over the neighbor's land. The court found that this granting of an easement is taking by the government without compensation. Schmitt says most rural Iowans realize the value of agriculture enough that they are willing to work out problems with their farm neighbors.

He stresses that under the Ag Area designation, farmers still were encouraged to make a concerted effort to eliminate as many nuisance problems as possible and use as many practical, modern-day science or technologies as possible to avert problems.

But now that specific nuisance protection is gone for large and small livestock and grain farmers alike, he explains.

Fast Track Fails Fast Track trade legislation was defeated in what National Pork Producers Council (NPPC) President Donna Reifschneider called "a disgraceful and depressing abandonment of American farmers and the nation's pork producers."

The bill was defeated in Congress 180 to 243. It sends "a clear signal to our competitors and the international community," says the NPPC leader, in what she refers to as the most important vote of this decade.

The economic crisis facing American farmers cries out for a progressive, long-term strategy that includes Fast Track negotiating authority, she says.

"We need to fully fund the International Monetary Fund and we need sanctions reform in addition to Fast Track," says Reifschneider. "But without Fast Track, we are simply sitting by the side of the highway, watching our competitors whiz by with agreement after agreement, costing us export sales and jobs."

For example, the Free Trade Agreement of the Americas is being negotiated without American participation. Also, Canada recentlynegotiated a bilateral agreement with Chile, lowering tariffs between the two nations.

Reifschneider declares: "Last year, exports accounted for $15.73 for every hog sold. Without Fast Track, it will simply be impossible for American producers to overcome high tariffs and other barriers, even though we are the world's low-cost producer."

Moratorium Moves Forward The North Carolina House of Representatives has voted to extend the ban on construction and expansion of hog farms in North Carolina. The ban was scheduled to end in March 1999. If the state Senate concurs with the House vote, the ban would be extended to September 1999.

Also, House bill 1480 requires contract growers to be registered and file notice of change of contract status. It also expands the use of new swine waste technology to improve air and water quality, explains Roger Bone, lobbyist for the North Carolina Pork Council.

Bone says the existing moratorium, passed during the last legislative session, has already cost farmers $100 million, based on data compiled by Kelly Zering, agricultural economist, North Carolina State University. Zering included in his costs things like the loss of investment and property tax base. He considered the multiplier effects that would have been generated by new hog farm construction.

More than $1 billion has been invested in new hog farms in North Carolina in the last decade, says Zering. Without new investment, there have been related lay-offs in businesses that supply construction and materials and equipment to hog farms.

In his report, Zering also looked at operation of these farms and processing of pork products from them.

Supporters of the ban say the extension is needed so researchers can figure out how to reduce the pollution and odor that large farms produce.

Intensive Training Program An intensive training program in production and management skills aimed at reviving the Illinois pork industry is being offered by the University of Illinois Extension Service. The Executive Pork Program (EPP) opens in April 1999 and extends through February 2001.

"This program will not simply be a rehash of traditional extension swine educational seminars," explains Gilbert Hollis, U of I extension swine specialist. "Participants will go through 12, three-day modules offered in a continuing education format."

The 12 modules offered include: swine industry trends, information and technology, computer applications; communications and human resources; leadership and organizational behavior; economics; financial management and records; marketing; swine genetics, Pork 2000 and meat quality; reproduction, records; environmental monitoring and legal issues; nutrition, pig growth, immunology and gene mapping; swine health and group presentations.

"This is a first-of-its-kind educational program and will facilitate the transfer of information and technology directly to pork producer leaders," says Hollis.

"Hog inventory in Illinois decreased over 40% between 1976 and 1996. The number of hog farms dropped by 45% between 1986 and 1996 and the state dropped from second to fourth in total pork production in the past four years," states Hollis. "Despite these decreases, hog production remains the third most important agricultural commodity in Illinois."

For more information, contact Hollis at 204 Animal Sciences Laboratory, 1207 W. Gregory Drive, University of Illinois, Urbana, IL 61801; telephone: 217/333-0013.

U.S. Hog Blockade At presstime, governors of six northern U.S. states agreed to halt what amounted to a blockade of Canadian hog and grain imports.

The action was initiated by South Dakota Gov. Bill Janklow in mid-September with the state banning trucks hauling Canadian hogs from passage through their state unless there is written certification that the hogs and grain meet certain guidelines. Hogs must be certified free of six drugs South Dakota officials say are banned for use in the U. S., but permitted in Canada. Grain shipments must be free of Karnal Bunt disease and not contain wild oats.

There was concern Canada was dumping low-priced agricultural commodities on the U.S. market because of favorable exchange rates. And there was a perception that U.S. inspections of Canadian imports are only cursory, while Canadian officials are thought to conduct the most in-depth inspections of U.S. imports allowed under trade laws.

The concerns drew the support of North Dakota, Montana, Idaho, Wyoming and Minnesota. These states stepped up inspections and took other steps to slow down Canadian truck traffic.

Canada's International Trade Minister Sergio Marchi, reported, "I am pleased that the U.S. federal government has intervened to stop the harassment." As a result, Canada withdrew plans to file trade complaints with the World Trade Organization and under the North American Free Trade Agreement (NAFTA). But Canada says they will reactivate the consultations if any U.S. state restricts or obstructs Canadian trucks again.

During the "blockade," Canadian ag officials charged that the U.S. action was politically motivated. "The inspection requirements established in mid-September for vehicles carrying Canadian hogs into the state of South Dakota are totally unjustified, are based on faulty information, and in our view represent a violation of NAFTA," says Edouard Asnong, president of the Canadian Pork Council.

Asnong says of the six drugs South Dakota's governor charges are used in Canada but are banned in the U.S., only one, dimetridazole, is available. It is used primarily in turkeys, but available for use by prescription only for treating swine dysentery in Canadian hogs. He added that Canadian hogs undergo stringent inspection standards including routine testing for antibiotics.

The six drug compounds in question are: dimetridazole, ipronidazole, nitroimidazoles, fluoroquinolones, glycopeptides and sulfamethazine.

Tom Burkgren, DVM, executive director of the American Association of Swine Practitioners, clarifies their status. He says dimetridazole, ipronidazole and the nitroimidazoles are banned from the U.S. Fluoroquinolones and glycopeptides are banned from extra-label drug use.

The fluoroquinolones have been approved for use in cattle and poultry in the U.S. As far as he knows, the glycopeptides have never been approved for use in livestock in either the U.S. or Canada. They are a widely used human antibiotic compound. Sulfamethazine has never been banned from use in livestock in the U.S. Sulfonamide drugs are banned from use in lactating dairy cattle, except for certain approved uses, says Burkgren.

Missouri Ag Conference The annual Commercial Agriculture Institute is set for Nov. 11-12 at the Ramada Inn, Columbia, MO.

Focus is "Cost Effective Strategies During Times of Financial Crisis."

For more details contact Joy Williams, conference organizer, at 573/882-9556.

NSIF Conference National Swine Improvement Federation (NSIF) Conference and Annual Meeting is slated for Dec. 4-5 at the Marriott Hotel, East Lansing, MI.

For a copy of the complete program plus registration information, contact NSIF, 203 Polk Hall, Box 7621, North Carolina State University, Raleigh, NC 27695-7621; phone: 919/851-6222; fax: 919/515-6316 or by accessing NSIF website at: mark.asci.ncsu.edu/NSIF/

Hotel reservation deadline is Nov. 3 for the $85 rate at the Marriott, 517/337-4440.

Barrow Show Results Grand champion of the National Barrow Show (NBS) truckload division carcass contest at Austin, MN, was W-D Swine Farm, Modesto, CA, with six Hampshire-sired crossbred hogs. The entry placed second live in the heavyweight class.

Carcass winners were selected based on average percent of lean. W-D Swine Farm's truckload entry averaged 59.20% lean, 187.1 lb. carcass weight, 34.1 in. length, .38 in. 10th rib backfat and 7.49 sq. in. loineye area.

Twenty-two Super Sire and 30 NBS Sire awards were presented in the NBS Progeny Test conducted in the spring. Test averages for both groups this year were: 1.79 average daily gain; 1.18 in. 10th rib backfat; 6.37 sq. in. loineye area; 56.80 muscle quality score and 7.50 soundness score.

In total, 333 boars and gilts were sold, bringing $375,070.

Animal Feeding Guidelines A national plan to deal with environmental issues from animal feeding operations was released by the Environmental Protection Agency and USDA.

The Unified National Strategy for Animal Feeding Operations (AFO) includes nutrient management requirements for all sizes of operations.

About 95% of the livestock operations in the U.S. will be able to participate in the program voluntarily with help from USDA to put these plans into action.

Growth & Composition

Six genetic types were used in the Quality Lean Growth Modeling project to represent a range in average daily gain, backfat deposition and loineye area. Genetic type classification was explained in the previous article by Goodwin and is abbreviated in the adjoining key.

The results presented here are based on the ultrasound scanning backfat and loin muscle measures taken every 2-3 weeks during the test period. Pig weights were taken at each scanning. The rate at which traits changed were measured for the total test period at the three respective off-test weights (90-250 lb., 90-290 lb., 90-330 lb.). The rates of growth, backfat and loineye area were estimated for each pig. Those rates were used for the QLGM analysis. Other authors will show rates of change for intervals during the growth period.

Table 1 presents rates of increase in body weight (average daily gain), backfat and loineye area for the six genetic types measured in the QLGM project.

Line A clearly deposited fat at a faster rate and had a slower rate of increase in loineye area (LEA) with an intermediate rate of body growth. In contrast, line D had the highest rate of body growth but was intermediate for backfat and loineye area increases. Lines B, E and F had the lowest average daily gains but had lower fat deposition and higher increases in loineye area. Line C had the second highest rate of body growth, the second lowest rate of fat deposition and ranked third for highest rate of increase in loineye area.

Table 1 clearly shows there were marked differences among genetic types for changes in body weight, backfat and loineye area.

Producers wishing to use this information need to know which of the genetic types represented here most closely matches the hogs in their operations.

In order to more accurately establish genetic type, randomly select 50 or more animals in your herd. Weigh them and measure their backfat and loineye area at least twice between 100 and 250 lb. More frequent measurements add to the accuracy.

Remember that you need at least two different genetic types, diets, environments, etc. to have a comparison. The most difficult part of setting up a comparison is trying to identify genetic type since most producers have only one type to test. One option to obtaining a second type for comparative purposes is to get boar semen from a defined genetic type, breed your sows, then include their progeny in your trial as a control. Examples of defined genetic types would include the lines tested in the NPPC Sire Line National Genetic Evaluation Program (NGEP). Berkshire, Duroc, Hampshire, Danbred and Newsham Hybrids pigs were defined in that test.

For example, if you want to conduct an on-farm test to compare growth rate, then Duroc semen would be useful to produce the test pigs needed. Likewise, if you wish to compare meat quality traits, then Berkshire semen would be a good choice for the test pig comparison. Work with your semen supplier to identify genetic lines that will provide pigs for a more accurate comparison.

Additionally, sex-specific tests and replication of your trial will add to the accuracy. The rate of change in these traits, not absolute values, will provide you with the information needed for genetic classification.

Remember also, to account for your nutritional program when assigning genetic type, as diet will affect the traits represented.

Protein's Impact Four nutritional programs were fed in which energy, minerals and vitamins were held constant within the weight ranges. However, lysine levels differed between the four diets. Diet 1 contained the highest lysine level (exceeding NRC standards), while diet 4 had the lowest lysine level (deficient by NRC standards). Lysine levels with each nutritional program were adjusted as pigs grew. (See Goodwin's Table 7, page 24). The protein (lysine) source in all diets was corn and soybean meal.

Table 2 gives the rates of change in body weight (average daily gain), backfat and loineye area as influenced by the four lysine levels fed. Only the lowest level of lysine (diet 4) influenced body weight gain. However, backfat tended to increase as lysine level decreased. Pork producers may wish to feed higher levels of protein (lysine) to get leaner hogs for packer buying programs. However, the economics of this decision must be scrutinized, as frequently changing costs will determine whether the change is a profitable one.

High and low levels of lysine created less muscle growth than intermediate levels of lysine.

In general, for the average pig in the trial, diet 2 provided the best combination of growth, backfat deposition and loineye area increase.

Market Weight Impact Pigs were assigned to one of three off-test market weights when they were delivered to test groups. Designated off-test weights were 250, 290 or 330 lb. Rates of change in body weight, backfat and loineye area for the total trial period are shown in Table 3.

The table shows there were no differences in average daily gain (ADG) for pigs marketed at the three weights. However, backfat deposition was higher for the two heavier weights. Rates of loineye area increase were similar for pigs marketed at 250 and 290 lb., but pigs marketed at 330 lb. had higher rates of increase in LEA. There were no interactions between market weight and either diet or genetic type. Thus, similar results for diet and genetic type were found regardless of market weight.

These results also show that rates of body growth, backfat deposition and LEA growth did not change markedly among the different genetic types and/or diets as market weights increased. If you know the rates of change in these traits, you can predict their values for each end weight of any genetic type. Other authors will address rates of change during specific intervals, which may help fine-tune feeding and/or marketing programs further.

Growth Rate Differences If you have identified your pigs' genetic type, taking into consideration the diets fed to those pigs when classifying them, you may use Tables 4 through 7 to help guide you toward matching diets to your goals for growth rate, backfat and loineye size. Table 4 presents the genetic type by diet effects for average daily gain. Remember, references to a diet, by number, covers the four nutritional phase-feeding programs fed from 90 lb. to the designated off-test weight. (250, 290, 330 lb., respectively. (Review QLGM Nutritional Programs, Table 7, page 24).

Except for line A, diet 1 produced the highest ADG. Line C had a marginally higher gain with diet 2. All other lines had reduced ADG as protein in the diet decreased.

If your lines resemble line A, you could use diets 2, 3 or 4 to achieve the fastest growth rates, if that is your goal. For the other genetic types, differences among diets 1, 2 and 3 are small and of little importance.

Thus, only the fattest line responded favorably to low lysine levels while only the lowest lysine level had an important impact on the faster-growing and/or leaner pigs. Therefore, producers have a relatively wide range of diet choices to maximize profits.

Backfat Variables Rates of change in backfat deposition by genetic type and diet are shown in Table 5.

All genetic types tended to have faster rates of backfat deposition as protein level in the diet decreased. Lines with high rates of fat deposition and low rates of muscle increases (lines A and D) deposited fat faster. Similarly, lines with low rates of fat deposition and high rates of muscle increase (lines B and E) also responded to lower protein levels by depositing fat quicker. The effect of protein level on backfat deposition in lines C and F were small, however.

It is most interesting to note that lower protein in the diet had essentially the same effect on the fatter lines as it did on the leaner lines. Only line C, a faster growing line with intermediate fat deposition, and line F, a slower growing line with intermediate fat deposition, were unaffected by changes in protein in the diet.

Based on rate of fat deposition, you would choose diet 1 for lines A and B. Diets 1 and 2 are of equal value for lines D and E, while lines C and F did best on diet 2. Again, the adjoining key can help you classify your market hog type if you have not conducted on-farm tests to help classify your genetic type.

Loineye Dilemma Rates of change in LEA were perplexing because intermediate levels of protein (diets 2 and 3) resulted in faster increases in LEA for all genetic types. Diet 4 was inferior for all genetic lines except line E, which had the lowest rate of LEA increase on diet 1. The relatively slow-growing, high-muscle line, line B showed little change in muscle growth as protein level changed. In contrast, line E, which was also slow growing with good muscle development, had a very low rate of muscle growth on high protein but did well on the other diets.

All lines tended to have similar loineye muscle growth at the two intermediate levels of protein. A general recommendation would be to feed diets 2 or 3 for best LEA growth.

Sex Differences Sex significantly influenced ADG, backfat and LEA (Table 8).

Gilts grew slower, had lower rates of fat deposition and slightly higher increments of loineye area. The effects on backfat for each sex were essentially the same as changing diets.

However, changes in the diet did affect the two sexes differently. Only very small changes in ADG were evident for barrows on the different diets. However, ADG for gilts tended to decrease as protein levels decreased (Table 9). This might suggest the need for higher protein levels for gilts.

Sex effects on backfat were somewhat different for the different genetic groups (Table 10). Sex differences were quite similar for lines B, C, D and E.

On the other hand, two lines (A and F), which tended to be relatively slow growing with moderate to high fat deposition, had large differences between the sexes for rate of fat deposition.

This observation reinforces the need to consider sex differences when on-farm trials are conducted, particularly when genetic types have a large difference between barrowsand gilts.

Conclusions In summary, marketing pigs at 250, 290 or 330 lb. had little effect on rates of change in body weight or loineye area during the total growth period. Marketing at these weights did not interact with genetic type or diet. In other words, lean pigs stayed leaner and fat pigs were fatter at all weights.

Both genetic type and diet influenced the rates of change in body weight, backfat and LEA. The rate of backfat deposition was higher at heavier weights. Further, significant interactions existed between genetic type and diet, such as the fattest type (line A) growing fastest on lower protein diets.

The choices of which diet to use for a genetic type depend on which trait you want to emphasize - body weight (ADG), backfat or LEA.

Table 7 presents a summary of diet(s) recommended for each genetic type for each of the respective traits. Again, the nutritional program differences are presented in Goodwin's article.

Diets 3 and 4 would probably never be recommended. Diet 2 appears to be the best general recommendation, but one may choose a diet depending on genetic type and the importance placed on a trait.

Further, these recommendations are based solely on performance; economics have not been considered.

Packer buying systems and the value of feed efficiency and growth rate (addressed by other authors) will help determine the nutritional programs offering the most profitable returns.

Feed Intake: Impact On Lean Growth & Lean Efficicney

Costs of growing pigs from weaning to market weight are determined largely by the amount of feed they consume and their rate of growth. Average daily feed intake is an expression of appetite. When carcass weights are within optimum ranges, value is determined by percentage lean. Therefore, rapid and efficient lean growth is important in pig production systems.

Protein requirements of pigs decrease as they grow. Thus, phase-feeding, or adjusting dietary protein intake during intervals of the growing period, is commonly used to reduce feed costs. Further, protein requirements differ for barrows and gilts because the sexes differ in appetite and in rate and composition of growth. Both barrows and gilts become increasingly less efficient in converting feed to weight as they get heavier. Thus, dietary protein concentrations and slaughter weights for optimum efficiency of lean growth are different for barrows and gilts.

Different selection strategies can produce genetic lines with different lean and fat growth curves and different appetites. Heavy emphasis on average daily gain will increase appetite. Whereas, heavy emphasis on reducing backfat will decrease appetite. Furthermore, selection strictly for decreased feed conversion ratio (feed/gain) will improve feed/gain ratios and decrease rate of fat deposition but will also decrease appetite and rate of gain.

Most selection strategies do not emphasize only one trait, but rather utilize an index of several traits weighted for some overall breeding objective. However, these indexes are usually designed uniquely for the role of each breed or line in a crossbreeding system. These different selection strategies, employed in breed and line development, cause genetic lines to have different appetites, different growth rates, and different rates of backfat and lean deposition. Therefore, the feeding strategy and slaughter weight that optimizes economic efficiency of lean growth may also differ across breeds and genetic lines of pigs.

In this article, feed intake, growth and efficiency of growth of pigs in the Quality Lean Growth Modeling (QLGM) project are presented. Genetic lines are characterized according to their biological type - mainly by their appetite (daily feed intake), rate of growth, and percentage carcass lean at different slaughter weights. Effects of diet and slaughter weight on these characteristics are presented.

Procedural Review Description of the genetic lines, the diets used, and management of the pigs are described in Goodwin's article (beginning on page 18). But a brief review is helpful to better understand the data in this report.

The pigs were samples from six genetic lines, as described in Tables 1 and 2, page 20. Sampling of lines was not done in a way required for valid genetic comparisons among lines. Therefore, each line is identified by a letter, A through F. To maintain anonymity they were shuffled and placed in the order listed in Goodwin's Table 4 (page 22) and abbreviated in the adjoining Key to Genetic Line Classification.

The six lines were selected, based on previous studies, to provide a relatively broad range of biological types for appetite, rate and composition of growth, and meat quality traits.

For example, line A was known to have a large appetite and to be fatter than other lines, so they ranked "high" for appetite and "low" for their less desirable backfat.

Line D was known to have appetite similar to that of line A, but to have greater growth rate and less fat. Thus, lines A and D were chosen because they differ in rate and efficiency of lean growth, but have similar appetites.

Line B was known to be lean with low appetite and moderate growth rate, and thus, to have good rate and efficiency of lean growth.

Lines C, E and F were expected to differ in component traits such as average daily gain, backfat and perhaps feed intake. The lines also are known to differ in muscle quality characteristics but these differences are not pertinent to discussions in this article.

For the most part, lines performed as expected based on previous data, but some deviations occurred, presumably because the sampling process did not duplicate that used in previous evaluations.

Diets are described in Table 7, page 24. They differed in amount of lysine. Beginning when pigs were placed on test at 90 lb., the high-lysine diet contained 1.25% lysine and lysine was decreased in increments of .15% to the low-lysine diet with .8% lysine. This reduction in lysine was accomplished by reducing the amount of soybean meal and increasing corn in the diets. Further, the amount of lysine in each diet was reduced by .15% as pigs attained pre-specified weights.

From the start of the test at 90 lb., pigs were fed the respective diet with the most lysine until they weighed 140 lb. Incremental reductions in dietary lysine occurred at gain intervals of 50 lb. - in other words, when the pigs reached weights of 140, 190 and 240 lb. Thus, there were four feeding periods for each pig with a .15% reduction in dietary lysine between each period, the last period being from 240 lb. to final off-test weight.

Pigs within a pen were all of one genetic line, but contained approximately an equal number of barrows and gilts. Within pen and sex, pigs were randomly assigned to be slaughtered at 250, 290 or 330 lb. They were individually removed from pens as they attained target slaughter weights.

The FIRE system (Feed Intake Recording Equipment from Osborne Industries) was used to record daily feed intake of each pig. Also, each pig was weighed at regular intervals beginning at 90 lb. until it attained its designated slaughter weight. Pen feed consumption was recorded for each period that corresponded to the dietary changes. The FIRE data were not available for preparation of this report. Therefore, analyses were done on a pen basis. Because pen averages were used in analyses, the effects of sex could not be evaluated. Also, because the average off-test weight was approximately the same for pigs in each pen, the effects of weight were evaluated by considering changes across the specific weight intervals corresponding to the four distinct periods.

Only two carcass traits are considered in this report, tenth rib backfat, measured off the midline on chilled carcasses, and percentage carcass lean, which was predicted from Fat-O-Meater measurements on chilled carcasses. These traits were used to relate differences in rate of growth, feed intake and feed conversion ratio to composition of the pigs.

Analyzing Results The data considered in this article include pen average daily feed intake, pen average daily gain, and pen feed conversion ratio (feed/gain) during each of the three test groups (from March 1996 through November 1997), and tenth rib backfat and percentage lean in carcasses.

There were a total of 394 pen/period records. Pen/period records included 3 test groups x 35 pens/group x 4 test periods = 420. Of the 420 records, hospital pens and a few pens with incomplete data brought the total down to 394.

Tenth rib backfat data were analyzed on 1,554 pigs and carcass lean was analyzed for 1,195 pigs. Analyses of pen averages were conducted to investigate effects of genetic line, diet, growth period (which corresponded to intervals of body weight change), and the interaction among these effects. Growth periods were 90-140 lb., 141-190 lb., 191-240 lb. and 241 to end weight for each pen since data is on a pen basis.

Backfat and percentage carcass lean were subjected to similar analyses, but effects of actual slaughter weights of 250, 290 and 330 lb., rather than the period of growth, were considered. Results are presented in tables and graphs to illustrate responses across these combinations of effects.

Feed Intake Analysis Average daily feed intake is an expression of appetite (Figures 1, 2 and 3). Figure 1 illustrates feed intake for each genetic line averaged across diets during each growth period. Figure 2 shows each diet averaged across genetic lines during each growth period. And, Figure 3 illustrates each line-by-diet combination averaged across periods.

Effects of line, diet and growth period were all significant (P<.01), and there was a significant interaction between genetic lines and periods.

There was a linear increase in daily feed intake as pigs increased in weight. The pattern was similar for pigs of each line, but the increase was greatest for lines A and D, the high appetite lines.

Daily feed intake reached a plateau in line E pigs as they ate the same amount of feed during periods 3 and 4 (P3, P4).

On average, pigs consumed 4.1, 5.3, 6.0 and 6.7 lb. of feed, respectively, during the four periods. Rate of increase in daily consumption was less for lines with lower appetite (Figure 1), but the proportional increase above average intake in the preceding period was similar for each line with the exception noted for line E.

Pigs fed diet 1, the high lysine diet, consumed more feed per day than pigs eating other diets (Figure 2). The average across periods was 5.8 lb. of feed per day for diet 1, and 5.5, 5.5, and 5.3 lb. per day for diets 2, 3 and 4, respectively. The increase in daily feed intake as weights increased was similar for pigs consuming each diet.

Pigs of line A, a high appetite line, consumed more of diet 4, the low lysine diet, than of the other diets (Figure 3). Lines B, D, E and F tended to consume less feed per day as lysine in the diet decreased. This pattern looks much like an interaction. However, the test of the line-by-diet interaction did not approach significance (P>.3). Therefore, the observed differences among lines on the different diets are probably due to sampling and not to real biological differences. The conclusion is that line differences in feed intake were consistent across diets.

Average Daily Gain Overall, line D had significantly greater average daily gain than all other lines (Figure 4). The other lines did not differ significantly.

Daily gain also differed significantly across periods. It was equal during P1 and P2 (1.69 lb./day), and then decreased in P3 (1.57 lb./day) and P4 (1.53 lb./day). Although it looks as though there might have been an interaction because line A had the greatest gain during period 4 and daily gain of line F started to decline in period 2, this interaction was not significant.

The conclusion is that, on average, pigs of all lines make their most rapid gains during weight intervals that correspond to periods 1 and 2 (90 to 190 lb.), and rate of gain declines thereafter as weight increases.

Average daily gains for pigs on each diet are illustrated in Figure 5. The pattern across periods is the same as described for Figure 4. Daily gains differed significantly for pigs on diets 3 and 4. Pigs eating diet 3 gained fastest (1.66 lb./day) and pigs eating diet 4 gained the least (1.56 lb./day) - a tenth of a pound difference, which has both economic and pig flow implications. Daily gain for pigs eating diets 1 and 2 were intermediate (1.63 lb./day) and did not differ significantly from gains for pigs on either diets 3 or 4.

Average daily gain for pigs of each line eating each diet are illustrated in Figure 6. The line-by-diet interaction was not significant. Therefore, differences between lines were consistent across diets. This finding is somewhat surprising as pigs with quite different appetites and composition of growth might be expected to have different average daily gains as dietary lysine changes. Specific tests of differences among lines on the different diets also did not reveal any interactions. Therefore, the observed variation in average daily gain for lines across diets was probably due to sampling. Pigs of all lines responded similarly to the dietary protein changes used in this experiment.

Feed Conversion Feed-to-gain ratios for pigs of each line at each period are illustrated in Figure 7. There were significant differences among genetic lines, and all conversion ratios at each growth period differed statistically from each other.

Lines E and B were most efficient, averaging 3.35 and 3.36 lb. feed/lb. of gain. Their average was statistically better than that of line A (average = 3.70), line C (average = 3.61) and line F (average = 3.57). Although the average for line D was greater (3.46 lb. feed/lb. gain) than for lines E and B, the difference was not significant, nor did the line D differ from lines F and C, but line D was significantly more efficient than line A. Average efficiency for lines A, C and F did not differ significantly.

Feed efficiency increased (got worse) linearly over periods. It averaged 2.48, 3.25, 3.87 and 4.45 lb. feed/lb. gain in periods 1 to 4, respectively.

Diet interactions with feed conversion were similar to diet interactions with average daily gain (Figure 8). Pigs eating diet 3 gained weight most efficiently (3.38 lb. feed/lb. gain). However, their efficiency did not differ significantly from that of pigs eating diet 2 (3.43), but was statistically better than that of pigs eating diet 4 (3.54) and diet 1 (3.68). Efficiency of pigs eating diets 2 and 4 did not differ significantly, but pigs eating diet 1 were significantly less efficient than pigs eating diets 2, 3 or 4. There was no interaction as differences among diets were very consistent across periods.

Feed conversion for pigs of each line eating each diet are illustrated in Figure 9. Again, line by diet interactions were not significant, as differences among lines were consistent across all diets.

Carcass Lean, Backfat Percentage carcass lean and tenth rib backfat for pigs of each line and diet at each slaughter weight are in Table 1 (page 46). Lines ranked similarly in percentage lean at each weight.

Lines B and E were consistently leanest; line A was fattest. The other lines were intermediate to these two groups. Differences between lines of pigs in percentage lean can be expected to be similar at slaughter weights between 250 and 330 lb.

Final slaughter weight had a significant effect on percentage carcass lean and on backfat thickness. The average percentage lean was 52.2% at 250 lb., 50.8% at 290 lb. and 49.6% at 330 lb. Tenth rib backfat average was 1.00, 1.17 and 1.28 in., respectively, at the three slaughter weights.

There was a linear increase in backfat and a linear decrease in percentage lean as slaughter weight increased above 250 lb. Each additional 40 lb. of live weight brought with it an average increase of .14 in. backfat and a decrease of 1.3% in carcass lean. The increase in backfat and decrease in percentage lean with increasing slaughter weight was similar in all lines.

Diets significantly affected percentage carcass lean and backfat thickness. Carcasses of pigs eating diets 1, 2 and 3 had similar backfat and percentage lean at all three slaughter weights. Diet 4 produced significantly fatter carcasses at all weights.

The only significant line-by-diet interaction was for percentage carcass lean at 290-lb. slaughter weight. The exact cause of this interaction is not clear. It appears to be mostly a change in magnitude of differences among lines, as lines ranked similarly on each diet. If this interaction were of biological importance we would expect to see a similar interaction at either, or both, of the 250 and 330 lb. slaughter weights. Also, the interaction was not significant for tenth rib backfat, adding additional evidence that it may not be biologically important.

What We've Learned Differences among genetic lines in feed intake, growth rate, feed conversion and carcass composition, as pigs increased in weight and while consuming diets with different amounts of lysine, were remarkably consistent.

Pigs consumed more feed per day when fed diet 1, the diet with the most lysine. But, the pigs neither grew faster nor developed carcasses with more lean while eating this diet. This result was consistent across lines and over all weight intervals. Therefore, it seems that diet 1 contained excess lysine for pigs of all genetic lines and, as such, did not promote greater nor more efficient lean growth in any of them.

Feed conversion was markedly poorer when pigs consumed diet 4. Also, these pigs had carcasses with more backfat and less lean than pigs consuming the other diets. Therefore, although efficiency of lean growth was not studied here, it was most certainly less for pigs of all lines when they received diet 4.

It appears that when all traits are considered, optimum performance for pigs of all lines was achieved when they consumed diets 2 and 3. Additional economic analyses of these data using individual feed intake records to determine whether there is an optimum diet and slaughter weight for each genetic line are needed.

Optimum slaughter weight depends on market price, costs of each additional increment of weight gain and the effect increasing weight has on composition. No attempt to determine this optimum for pigs of each line was made in this study.

However, pigs became quite inefficient at converting feed to live weight as weights increased above 250 lb. Further, daily rate of gain declined for pigs of all lines as weights increased above 190 lb. Even with inexpensive feed, it appears that costs of gain increase substantially as pigs are taken to heavy slaughter weights. The problem is further compounded by the fact that percentage carcass lean decreases with increasing weight.

Optimum slaughter weight is certainly different for pigs of the different genetic lines - lower for fat lines than for leaner lines.

Data reported here are averages for barrows and gilts. Additional analyses of individual feed intake to determine optimum diets and slaughter weights for barrows and gilts of each genetic line are needed. However, the data reported here can be used as a guide by producers. By matching performance of the line of pigs used by the producer to those of one of the biological types studied here, the effect of changing dietary lysine and the extra time and feed needed to grow pigs to heavy weights can be estimated.