Living through the volatility of feed prices over the last two years has heightened producers' awareness of the need for continual improvement in the efficiency of feed use.
Efficient use of feed means different things to different people. Nutritionists consider dietary energy levels, particle size and feed processing.
Swine veterinarians may think about the impact of disease and health status.
Producers in the barn may think about feeder adjustment, impacts of weaning age or productivity levels.
Geneticists may consider sire lines and the contribution of the sow to whole herd feed efficiency.
Accountants may be focused on the dollars and cents.
As farm owners, all of these factors must be considered to reach the overall goal of more efficiently using a resource that is much more valuable today than just a few short years ago — feed.
Of course, decisions on optimal diets and the impact of the diet on feed efficiency cannot be made in a vacuum. The profitability of the entire production system must be considered.
When feed prices are high and alternative ingredients are available, the most profitable decision for some production systems may be to reduce the energy level, which will reduce growth rate and increase days to market. This scenario was rarely the best option in past years, because finishing space was not available to make reducing growth rate a profitable decision.
However, a reduction in the U.S. swine herd, coupled with an increase in finishing barn availability, will make this the most profitable option for some production systems. These changes make benchmarking and comparing feed efficiency from one production system to another very difficult. A clear understanding of all of the drivers of profitability is required to truly determine whether a system is using their feed resources efficiently.
Measuring Efficiency of Feed Use
In order to make improvements, we have to know what to measure. When discussing feed efficiency, we naturally think about closeout feed efficiency for a group of pigs, where we have accounted for the pounds of feed delivered to a group of pigs. The pounds delivered includes all feed consumed or wasted by the pigs.
Traditionally, the other half of the equation is the weight gain of the pig, which is simply the weight of pigs at the end of the feeding period minus the weight at the beginning of the period. Closeout feed efficiency is a good place to start and, when the subject of focus, has led many production systems to continual improvement over time.
When most diets were corn-soybean meal-based, this traditional method of measuring feed efficiency was probably sufficient. However, the introduction of other ingredients to swine diets can greatly impact the energy value of the diet and, potentially, the yield of the pigs. Thus, for future measurements, we will need to change the numerator of the equation from feed to the amount of “energy that was delivered to the pigs.” Similarly, the denominator may need to change from total weight gained to “pounds of carcass weight gained” (see Figure 1 ).
There are many different ways to measure the energy density of a diet, which are covered in detail by John Patience of Iowa State University, on page 10 in this Blueprint.
Feed efficiency for a group of nursery or finishing pigs is often more easily measured and tracked than trying to measure and monitor whole herd feed use. To truly improve the efficiency of all feed used on the swine farm, a clear accounting of sow gestation, lactation and gilt developer feed must also take place.
Tracking use and cost of these feed categories on a per-sow, per-marketed pig, and per-pound-of-carcass weight basis will allow for continual improvement and illustrate the importance of sow productivity in reducing the impact of these feed costs on the cost burden carried by each pig marketed.
Factors Influencing Efficient Feed Use
Any factor that influences the numerator (feed or calories) or denominator (weight produced) in the efficiency equation is important to consider when trying to improve the efficiency of feed use.
Sire and dam genetics have a major impact on efficiency of feed use. Genetics determine the upper limit for the pigs' potential to convert calories into carcass lean. Genetics can also dictate the pigs produced per sow per year, which profoundly impacts whole herd feed conversion. The genetic contribution to the efficient use of feed is discussed by Jim Schneider beginning on page 22 of this Blueprint edition.
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Dietary energy level
Because higher energy diets contain more calories, less feed is required for each unit of weight gain or per sow per day when a higher energy diet is fed. This is a simple concept, but often overlooked when comparing feed efficiency across production systems or even between groups within a production system.
Thus, dietary ingredients that lower the energy density of the diet have a direct impact on feed efficiency by increasing the pounds of feed required for each pound of gain. Because reducing the dietary energy level also can lower growth rate, low-energy diets can also indirectly increase feed-to-gain (F/G) by decreasing the denominator in the F/G equation.
Other diet variables
If the diet is deficient in any nutrient, daily gain will be reduced and feed efficiency will suffer. Of all nutrients, deficiencies in amino acids have the greatest negative impact on feed efficiency. Amino acid levels (lysine being the first limiting amino acid in most diets) should be reviewed whenever feed efficiency is not achieving target levels.
If housed below its thermo-neutral zone, the pig will use feed as a heat source to keep warm instead of using it for growth, and feed efficiency will be poorer. The economic value of these tradeoffs must always be considered.
Diet form and processing
As covered in detail by Charles Stark in this Blueprint (page 16), pigs fed pelleted diets will have 3-6% better feed efficiency than those fed diets in meal form. The quality of the pellet and the particle size of the grain in the pellet dictate much of the range of the benefit.
Reducing particle size of ingredients in the diet (whether pelleted or meal form) increases available surface area for enzymes to work on the particles, which increases digestibility, making more energy available to the pig to improve feed conversion. For each 100 micron reduction in particle size, feed efficiency is improved by approximately 1.2%.
Equipment (feed wastage)
Feed wastage can occur in many areas on the farm. Poorly adjusted feeders or old feeders that cannot be adjusted increase feed wastage and, therefore, hurt feed efficiency. (See “Feeder Adjustments Optimize Growth, Reduce Feed Wastage,” page 34).
Other efficiency robbers may not be as noticeable at first glance. For example, removing and discarding good, dry feed from feeders in the farrowing house in order to offer sows fresh feed can be a tremendous waste of expensive feed. Some automatic lactation feeding systems waste a tremendous amount of feed by dropping feed into troughs that are already full.
Likewise, over-feeding gestating sows should be quantified as feed wastage because the expense occurs without a measurable benefit. In fact, the extra feed may actually do more harm than good.
Most diseases have a much greater impact on feed intake and average daily gain than on feed efficiency. For example, gastrointestinal maladies (porcine proliferative enteritis or ileitis, haemorrhagic bowel syndrome or HBS, etc.) may affect growth rate, but have less impact on feed efficiency. This is the reason that some groups of pigs can have very low daily gain and feed intake and still have good feed efficiency numbers.
However, diseases such as porcine circovirus, with high mortality rates late in the finishing stage, are devastating to whole-herd or finishing closeout feed efficiencies. Diseases that increase mortality reduce the weight generated from the group, while feed disappearance remains high, thereby resulting in poorer feed efficiency. Feed efficiency is increased by 1.5 to 2% for each 1% increase in mortality.
Diseases such as porcine circovirus that cause a tremendous immune response also reduce the efficiency of feed use directly, in addition to their impact on mortality. Immune activation diverts nutrients away from growth towards the immune system, which results in poorer feed efficiency. For many diseases, this effect is too small to directly measure a change in feed efficiency; however, this impact is much greater and more measurable for other diseases.
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Because the weight gained in gilts has a higher lean-to-fat ratio, less feed is required for each pound of weight gain in gilts compared to barrows. Although the exact difference varies by genetic line, gilts typically are 3 to 6% more feed efficient in the finishing period than barrows. Similarly, boars are more efficient to feed than gilts.
When examining whole herd feed efficiency, the productivity of the sow herd directly determines the number of pigs that sow feed use and costs can be spread over. As an example, let's consider two identical farms that use 2,100 lb. of feed per sow per year. If one of the farms markets 18 pigs/sow/year, each pig marketed would carry the cost of 117 lb. of sow feed. If the other farm marketed 22 pigs/sow/year, each pig marketed would carry only 95 lb. of sow feed.
Because feed efficiency becomes poorer as pigs become heavier, the starting and ending weight of pigs must be considered when comparing closeout feed efficiency from one group or farm to another.
For example, feed efficiency increases by approximately 0.005 lb. for each 1-lb. increase in average starting and ending weights for the group. Thus, if two groups of pigs have the same starting weight, but one is marketed 10 lb. heavier than the other group, feed efficiency would be expected to be 0.05 higher for the heavier group, just because of the market weight. On an energy basis, the 0.005 lb. would be equivalent to 7.5 kcal more metabolizable energy for each 1-lb. increase in average starting or ending weight.
Although weaning age doesn't have much impact on feed efficiency, it can greatly impact other measures of efficiency of feed use, such as feed cost in the nursery, because lower complexity (and lower cost) diets are required as weaning age is increased.
Benchmarking Efficiency of Feed Use
Because so many factors influence feed efficiency, the best benchmarks are those developed within the production system. The overall goal of benchmarking is to make consistent, measurable improvement over time.
When comparing benchmark levels, adjustments must be made to account for the factors that influence feed efficiency, such as gender, diet form, dietary energy level and starting and ending weight, as discussed above.
The values provided in Table 1  offer intervention levels for closeout feed efficiency for nursery, finishing and wean-to-finish pigs. If the efficiency numbers for the production system are not better than these levels, reasons for this deficiency should be investigated.