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2005 Swine Research Review - Nutrition

Herd Health/Management The Impact of PRRS On Cost of Production Four pork industry analysts used a combination of techniques and data to project the current annual cost of porcine reproductive and respiratory syndrome (PRRS) to the U.S. swine industry. The USDA-National Animal Health Monitoring System (NAHMS) conducts a survey every five years to provide a valid demographic and descriptive survey


Out-of-Feed Events Impact Pig Performance

Producers are increasingly reducing the fineness of grind in pig rations in an effort to improve feed conversion and overall grow-finish performance.

However, finely ground diets could be producing out-of-feed events, due to bridging of feed in bulk bins and feeders. This can lead to an overall reduction in average daily gain.

Add to this the difficulties in placement and delivery of feed orders from toll mills, and the possibility of many out-of-feed events occurring during the grow-finish phase of production increases.

To test the impact of out-of-feed events, 240, 17-day-old weaned pigs were shipped 200 miles to the University of Nebraska's Haskell Ag Lab in Concord, NE.

On arrival, 15 pigs were placed in each of 16, 8×14-ft., fully slotted pens in a naturally ventilated, wean-to-finish barn, providing 7.5 sq. ft./pig.

Only barrows were placed on test to avoid the influence of gilts urinating in feeders. The experimental treatments began six weeks postweaning and lasted for 109 days (nearly 16 weeks).

Table 1. Impact of Experimental Treatments on Pig Performance
Out of Feeda Particle Sizeb
Item Never Weekly Coarse Medium
No. pens 8 8 8 8
Pig weight, lb.
On test 53.2 51.3 52.3 52.2
Day 53 155.2 145.3 150.9 149.6
Day 109 261.8 251.5 257.6 255.7
Coefficient of variation of pig weight within pen, %
On test 17.4 16.1 16.3 17.3
Day 53 10.7 10.9 10.3 11.3
Day 109 8.1 8.2 7.5 8.8
Daily gain, lb.
On test — Day 53 1.92 1.77 1.86 1.84
Day 53 — Day 109 1.90 1.89 1.91 1.89
Overall 1.91 1.84 1.88 1.87
Daily feed intake, lb.
On test — Day 53 4.42 4.13 4.34 4.21
Day 53 — Day 109 6.57 6.47 6.67 6.36
Overall 5.52 5.33 5.54 5.31
On test — Day 53 2.30 2.33 2.34 2.29
Day 53 — Day 109 3.45 3.41 3.50 3.36
Overall 2.89 2.90 2.94 2.85
Carcass data, Tyson Fresh Meats, Madison, NE
Carcass wt., lb. 206.3 197.5 201.6 202.1
Fat depth, in. 1.02 0.97 0.98 1.00
Loin depth, in. 2.75 2.67 2.72 2.70
Lean, % 53.5 53.5 53.6 53.4
Pigs dead, no. 2 4 2 4
Removed, no. 1 1 0 2
< 205 lb., no. 2 4 2 4
aNever = never out of feed; Weekly = 20 hr-out-of feed on a random day each week.
bCoarse = average 1266 microns; Medium = average 1019 microns.

Four treatment combinations analyzed two nutritional factors: 1) out-of-feed events, never or weekly; and 2) feed particle size, coarse (1,266 microns) or medium (1,019 microns). Out-of-feed events consisted of a 20-hour period starting at 12 noon on a random day each week for the 16-week period.

During the first eight weeks, weekly out-of-feed events reduced average daily gain 0.15 lb./day, compared to the never out-of-feed treatment (Table 1), due to a reduction in daily feed intake. Total gain depression was 7.9 lb. for pigs experiencing weekly out-of-feed events. There was no impact on feed conversion efficiency.

In contrast, out-of-feed events had no effect on daily gain or feed conversion for the second, eight-week period of the experiment.

For the 109-day feeding trial, weekly, random, 20-hour out-of-feed events resulted in a 0.077/lb./day decrease in daily gain and a total loss of 8.4 lb./pig with no effect on feed conversion. Pigs adjusted to being out of feed in the second half of the experiment, though they never compensated for the loss in gain during the first half of the trial.

Decreasing particle size 247 microns (going from coarse to medium) resulted in a 3.1% improvement in overall feed conversion.

The experimental design did not produce any differences in skin lesion scores, a measure of animal welfare and injury from fighting at the feeder.

Also, there was no interaction of out-of-feed events and diet particle size.

“In production units that must sell pigs by a certain date, these data will allow producers to examine whether the improvement in feed conversion efficiency from finely ground diets overcomes the loss in weight gain from out-of-feed events that may be due to increased bridging of finely ground diets,” observes lead researcher Mike Brumm, University of Nebraska.

Researchers: Mike Brumm and Sheri Colgan, research technologist, University of Nebraska Northeast Research and Extension Center, Concord, NE. Contact Brumm by phone (402) 584-3816, fax (402) 584-3859 or e-mail

Sorting by Weight, Bumping Energy Improves Returns

Greater economic returns may be possible by dividing finishing pigs by weight, not sex, and then feeding a targeted, higher energy diet to lighter pigs, according to Kansas State University researchers.

Two studies have shown that adding 6% dietary fat to the lightest 50% of the finishing pig population increased average daily gain (ADG) and reduced the number of lightweight pigs sold. Researchers say by feeding 6% dietary fat to the light pigs and removing fat for heavy pigs, producers could increase profit margins when compared to feeding mixed populations of heavy and light pigs.

Table 1. Effects of Added Fat and Initial Sort on Growth Performance in Grow-Finish Pigs (Exp. 1)a
Main Effects
Fat Addition Weight
Item Fat No Fat Heavy Light Mixed
Average daily gain, lb.
Day 0 to 56 1.59 1.54 1.68 1.48 1.54
Day 56 to 88 1.90 1.83 1.90 1.83 1.85
Day 88 to 109 2.20 2.25 2.29 2.18 2.23
Overall 1.79 1.76 1.83 1.72 1.76
Average daily feed intake, lb.
Day 0 to 56 3.42 3.64 3.88 3.20 3.48
Day 56 to 88 4.98 5.42 5.53 4.92 5.16
Day 88 to 109 5.60 6.22 6.19 5.62 5.86
Overall 4.23 4.59 4.74 4.17 4.39
Day 0 to 56 2.16 2.38 2.33 2.27 2.22
Day 56 to 88 2.70 2.94 2.94 2.70 2.78
Day 88 to 109 2.56 2.78 2.70 2.56 2.63
Overall 2.38 2.63 2.56 2.44 2.50
aA total of 1,032 gilts (24 or 25 pigs/pen and seven pens/treatment) with an initial average weight of 67.7 lb.
Table 2. Effects of Added Fat and Initial Sort on Weight Variation, Carcass Traits, and Economic Value in Grow-Finish Pigs (Exp. 1)a
Main Effects
Fat Addition Weight
Item Fat No Fat Heavy Light Mixed
Weight, lb.
Day 0 67.7 67.8 76.5 59.1 67.7
Day 56 158.4 155.7 172.0 142.9 156.4
Day 88 219.1 215.1 233.6 201.8 216.1
Day 109 262.9 260.1 275.6 248.0 260.8
Weight, CVc
Day 0 12.27 11.87 8.72 11.85 15.65
Day 56 14.56 14.10 12.16 15.21 15.62
Day 88 12.74 11.89 10.23 13.06 13.67
Day 109 11.79 10.99 9.18 12.48 12.50
Average daily gain CV
Day 0 to 56 20.44 20.79 19.18 22.02 20.66
Day 56 to 88 16.55 15.43 14.86 15.76 17.34
Day 88 to 109 19.78 19.76 19.02 19.75 20.54
Overall 14.07 13.28 11.86 14.86 14.31
Carcass Traits
Backfat (mm) 0.57 0.57 0.59 0.56 0.57
Fatfree Lean Index 51.49 51.48 51.58 51.32 51.55
Lean, % 57.22 57.22 56.99 57.36 57.31
Loin Depth, cm 2.40 2.37 2.39 2.37 2.40
Economic Value
FC/lb. Gain, $ 0.168 0.163 0.168 0.159 0.163
Sort discount, $ -2.55 -2.28 -2.57 -2.08 -2.66
MOFb, $ 90.99 91.26 94.92 87.65 90.81
aA total of 1,032 gilts (24 or 25 pigs/pen and seven pens/treatment) with an initial average weight of 67.7 lb.
bMargin Over Feed; calculated using corn $2.16/bu, SBM $186.19, Fat $13.34/cwt, Carcass Base Price $45.39
cCV = Coefficient of Variation

Because U.S. packer matrices impose large discounts for lightweight pigs, any technology or management technique that reduces the number of lightweight pigs could result in a higher net return.

Researchers focused on reducing variation in a group of pigs by increasing growth rate of the lightest pigs, thus shifting this portion of the population to heavier weights. Researchers were striving to determine whether adding dietary fat to the diet of the lightest 50% of the pigs in a finishing barn could increase both ADG and economic return.

The first experiment was conducted with 1,232 gilts with an initial weight of 67.7 lb. The pigs were sorted into weight categories. Pigs were housed in pens of 24-25 pigs/pen. The second experiment included 1,176 gilts sorted by weight with 28 pigs/pen.

Diets were formulated in meal form and fed in three phases for both experiments. Pigs were weighed and feed disappearance was determined every 14 days.

The addition of fat to diets increased ADG in the first two periods of Experiment 1, and tended to increase growth for the overall study (Table 2). Adding fat also reduced feed intake and improved feed efficiency during each period.

Adding fat to diets increased ADG in lightweight pigs, but not in the heavyweight pigs in the first study. This interaction was unexpected, so a second study was conducted.

Table 3. Effects of Added Fat and Initial Sort on Growth and Variation of Growth in Grow-Finish Pigs (Exp. 2)a
Main Effects
Fat Addition Weight
Item Fat No Fat Heavy Light Mixed
Average daily gain, lb.
Day 0 to 49 1.87 1.79 1.85 1.79 1.83
Day 49 to 81 2.09 2.05 2.09 2.07 2.07
Day 81 to 95 2.18 2.12 2.27 2.03 2.12
Overall 1.98 1.92 1.96 1.92 1.94
Average daily feed intake, lb.
Day 0 to 49 4.19 4.45 4.52 4.10 4.32
Day 49 to 81 5.20 5.67 5.60 5.25 5.45
Day 81 to 95 6.00 6.53 6.57 5.95 6.26
Overall 5.05 5.47 5.73 4.81 5.22
Day 0 to 49 2.22 2.50 2.44 2.27 2.33
Day 49 to 81 2.44 2.78 2.70 2.50 2.56
Day 81 to 95 2.78 3.13 2.86 2.94 2.94
Overall 2.38 2.70 2.56 2.44 2.50
aA total of 1,176 gilts (28 pigs/pen and seven pens/treatment) with an initial average weight of 77.4 lb.
Table 4. Effects of Added Fat and Initial Sort on Weight Variation, Carcass Traits, and Economic Value in Grow-Finish Pigs (Exp. 2)a
Main Effects
Fat Addition Weight
Item Fat No Fat Heavy Light Mixed
Weight, lb.
Day 0 77.4 77.6 83.1 71.7 77.6
Day 49 168.7 164.7 174.1 159.2 166.9
Day 81 235.9 230.7 240.7 225.9 233.3
Day 95 264.5 258.9 269.3 254.2 261.7
Weight, CVc
Day 0 12.65 12.58 9.66 12.32 15.86
Day 49 10.86 11.06 8.74 11.12 13.02
Day 81 9.44 9.82 8.36 9.54 11.00
Day 95 8.60 8.93 7.35 9.22 9.71
Average daily gain CVc
Day 0 to 49 13.32 13.49 11.86 13.79 14.57
Day 49 to 81 12.57 15.32 14.91 13.31 13.62
Day 81 to 95 21.11 21.64 19.07 25.19 19.86
Overall 9.53 9.76 9.15 10.03 9.77
Economic Value
FC/lb. Gain, $ 0.163 0.159 0.168 0.159 0.163
Sort Discount, $ -3.08 -2.56 -3.35 -1.90 -3.22
MOFb, $ 93.30 92.59 96.28 90.13 92.42
aA total of 1,176 gilts (28 pigs/pen and seven pens/treatment) with an initial average weight of 77.4 lb.
bMargin Over Feed; calculated using corn $2.16/bu, SBM $186.19, Fat $13.34/cwt, Carcass Base Price $45.39
cCV = Coefficient of variation

In the second study, pigs fed diets with added fat had greater ADG through Day 49 of the study, and overall (Tables 3 and 4).

Adding fat also lowered average daily feed intake and improved feed efficiency during every period and for the overall study.

Similar to the first experiment, pigs sorted into heavy pens had greater ADG overall when compared to light or mixed pens. Lightweight pigs had a better overall feed efficiency compared with heavy or mixed pigs.

Researchers concluded that profitability in the lightest 50% of the pigs was increased by $1.46/pig in the first experiment, and $3.19/pig in the second experiment by feeding high-fat diets; average profit overall was $2.33/pig. Because this profit is only achieved on 50% of the pigs, it is worth $1.16/pig marketed, researchers noted.

Many nutritionists estimate that split-sex feeding within the same barn is worth $.50 to $.60/pig. The KSU results indicate that dividing the groups by initial weight, and feeding a higher energy diet to the lightest 50% of the pigs in order to increase growth rate, yields a greater return than dividing the group by sex. Large production systems could gain added benefits if pigs were fed by weight in addition to split-sex feeding benefits.

Researchers: Chad Hastad, Mike Tokach, Steve Dritz, DVM; Robert Goodband, Joel DeRouchey and Jim Nelssen, Kansas State University. Contact Tokach at (785) 532-2032 or e-mail

Impact of Nursery Diet Ingredients On Feed Flow

High concentrations of lactose and specialty protein sources in nursery pig diets can cause bridging in bins and feeders. Kansas State University researchers recently conducted two experiments to determine the effects of different lactose and specialty protein sources on the flow characteristics of a 70:30 corn-soybean meal-based nursery diet.

The first experiment focused on six lactose sources. Three sources were fine powdered whey permeates, and the other sources were coarse ground whey permeate, edible grade spray-dried whey, and a crystalline lactose source. Lactose sources were added at 0, 5, 10, 20 and 30% to the corn-soybean meal blend (Figure 1).

Researchers measured the maximum angle in which a pile of ingredient retained its slope, called the “angle of repose.” A large angle of repose represents a steeper slope and poorer flowability of the feed ingredient.

Increasing the inclusion of the lactose source showed good flowability; however, the coarse whey permeate had a much greater improvement in flowability.

The second experiment evaluated five specialty protein sources: spray-dried animal plasma in powdered and granulated form, spray-dried blood cells in powdered and granulated form, and select menhaden fish meal (Figure 2).

Specialty protein sources were added at 0, 2.5, 5, 7.5 and 10% to the 70:30 corn-soybean meal blend.

As powdered animal plasma and blood cells increased, the angle of repose increased, resulting in poorer flowability. Better flowability was achieved with the addition of granulated animal plasma and blood cells. Increasing fishmeal did not influence the flowability. The researchers concluded the greater flowability is observed with granulated specialty protein or coarsely ground lactose sources.

Lactose and specialty protein sources are often included in nursery pig diets to stimulate feed intake and improve growth performance. The researchers suggest adding granulated specialty protein sources to meal diets to improve feed flowability. Adding granular ingredients like Dairy Lac 80, Appetein, or granulated blood meal improve flowability.

Although the addition of granulated lactose and specialty protein sources to meal diets will increase feed cost slightly, they will improve feed flowability and can help decrease feed bridging in bins, feeders and other feed handling systems. Researchers are currently testing whether angle of repose can be used in feedmills to measure the relative flowability of meal diets to prevent problems in the field.

Researchers: Erin Carney, Crystal Groesbeck, Robert Goodband, Mike Tokach, Jim Nelssen and Steve Dritz, DVM. Contact Carney at (785) 532-1277 or e-mail

Measured Digestibility Values for DDGS Aid Diet Formulation

South Dakota State University (SDSU) researchers measured digestibility values for distiller's dried grains with solubles (DDGS) that demonstrate for the first time that DDGS has nearly the same energy content as corn. This discovery will reduce the cost of formulating diets with DDGS.

SDSU scientists took 10 samples of DDGS collected from ethanol plants in South Dakota and formulated 11 diets. One diet was corn-based, and the rest were formulated by mixing each of the 10 sources of DDGS and the corn diet in a 1:1 ratio.

Eleven growing pigs were placed on test at 64.5 lb. for 22 weeks in metabolism cages that permitted total, but separate, collections of urine and feces. Each pig was fed each diet for two weeks.

All samples of urine and feces were analyzed for concentrations of energy, crude protein and phosphorus, and the Apparent Total Tract Digestibility (ATTD) for energy, protein and phosphorus were calculated. Levels of digestible energy (DE) and metabolizable energy (ME) in each source of DDGS were also calculated.

Results are presented in Table 1. The average ATTD values recorded for energy, crude protein and phosphorus in DDGS were 76.8%, 83% and 59.1%, respectively. The energy and protein digestibility values are similar to those found in corn.

However, the phosphorus digestibility in DDGS is much higher than that of corn, reducing the need for monocalcium phosphate in the diet by 5 lb./ton of feed if 20% DDGS is included in the diet. That represents a savings of about $0.5/ton of feed.

The DE and ME values may vary among sources, but the experiment showed that the values are close to those of corn. The values for DE and ME in this experiment are 21% and 27%, greater than the values currently listed by the National Research Council.

Because energy values are similar to those found in corn, it eliminates the need to add extra oil to diets containing DDGS to maintain the same energy level.

“When pork producers and feed companies formulate diets with DDGS, they now have measured values for DE, ME and phosphorus digestibility to use in the formulas,” says lead SDSU researcher Hans Stein. “By using the energy value of DDGS, other nutrients may be included at ratios that match the energy in the diet. Therefore, diets containing DDGS can be more accurately formulated.”

Because values for phosphorus digestibility are now available, diets can be formulated without under- or oversupplying phosphorus, thus reducing the level of phosphorus excretion into the environment without lowering animal performance.

Researchers: H.H. Stein, C. Pedersen and M.G. Boersma, South Dakota State University. Contact Stein by phone (605) 688-5435, fax (605) 688-6170 or e-mail

Table 1. Apparent Total Tract Digestibility (ATTD) of Energy, Protein and Phosphorus, and Concentrations of Digestible Energy and Metabolizable Energy in Corn and in 10 Sources of DDGS Fed to Growing Pigsa
Item Corn Distiller's dried grains w/solubles (DDGS)
Average Range
ATTD, energy, % 90.4 76.8 73.9 to 82.8
ATTD, protein, % 81.5 83.0 77.1 to 87.5
ATTD, phosphorus, % 19.3 59.1 50.1 to 68.3
Digestible Energy, kcal/kg. Digestible Matter 4,090 4,191 4,015 to 4,555
Metabolizable Energy, kcal/kg. Digestible Matter 3,989 3,871 3,678 to 4,255
aData are means of 11 observations/treatment.

DDGS Boosts Sow Nutrition; Phytase Cuts Phosphorus Loss

High-producing lactating sows can thrive using 15% distiller's dried grains with solubles (DDGS) to help meet their nutritional needs.

Equally important, adding phytase to these DDGS-supplemented sow lactation diets reduced phytate phosphorus excretion levels over sows fed conventional sow rations or a complete DDGS ration without phytase.

Two studies were completed using Yorkshire × Landrace sows nursing 11 or more pigs/litter, weaned at 18 days of age.

The first study compared sows fed 15% DDGS with sows fed 5% beet pulp (BP). The diets contained the same amount of fiber, lysine (1.2%), calcium (0.9%) and phosphorus (0.84%).

Treatment did not influence lactation performance. Sows weaned 10.9 and 10.8 pigs/litter with an average gain of 8.4 and 8.6 lb./pig for the BP- and DDGS-fed sows, respectively. Weight loss during lactation was 13.6 lb. (BP) and 17.9 lb. (DDGS). Fecal phosphorus excretion decreased linearly for DDGS-fed sows.

In the second study, a 15% DDGS sow lactation diet was compared with three other diet formulations. The trial included a control group (typical corn-soy diet), control group plus phytase, control group with 17% of phosphorus supplied by 15% DDGS and this same DDGS diet plus phytase.

At 110 days of gestation, sows were gradually introduced to their lactation diet. Two days postfarrowing, litters were crossfostered to 11 pigs/litter and sows and litters were weighed. Fecal grab samples were collected from 48 sows (12/treatment) on Day 7, 14 and 18 of lactation. Litter weight gain (101.2, 101.9, 92.6 and 92.8 lb.) and sow weight loss (17.8, 15.8, 15.4 and 13.9 lb.) were not affected by the respective dietary treatments.

The phosphorus concentration in the feces was similar between treatments on Day 7, 14 or 18, but was reduced in sows fed all treatments on Days 14 and 18.

Significantly, however, fecal phytate phosphorus (the form of phosphorus in corn and soybeans) was reduced in sows fed the DDGS-phytase diet at Day 14 and 18, vs. sows fed the three other diets.

Researchers: G.M. Hill, D.L. Kirkpatrick, J.E. Link, M.L. Gibson, K. Karges and M.J. Rincker, Michigan State University; and Dakota Gold Research Assn. Contact Hill by phone (517) 355-9676, fax (517) 432-0190 or e-mail

Feeding Trials Support Added Fat Benefits, Discount Genetic Link

Two experiments conducted by the University of Nebraska confirmed the benefits of added fat to grow-finish performance and discounted any genetic link between sire line and dietary treatment.

In each experiment, rations consisted of corn-soybean meal-based diets with no added fat and corn-soy diets with added fat. The level of added fat ranged from 3.75% for the 40- to 70-lb. weight period to 1.5% for pigs over 220 lb.

Pigs fed in the experiments were progeny of Danbred females bred to four different Danbred sire lines.

Feeding trials showed there were no interactions between sire line and dietary treatment in either experiment. And there was no effect of dietary treatment on daily gain.

Feed conversion improved 6.8% in the first experiment with the added fat vs. the control diet, but only 3.7% improvement for the added fat group in the second experiment.

The lack of daily gain response, when combined with a lack of genetic interaction, suggests that for at least these genetic lines, daily gain is not a consideration as to the use of fat in grow-finish diets.

Researchers: Mike Brumm, University of Nebraska; Larry Himmelberg, formerly of Danbred; and Tom Rathke and John Sonderman of Danbred North America. Contact Brumm by phone (402) 584-3816, fax (402) 584-3859 or e-mail