Thus, feeding different diets based on initial body weight going into the finisher may help reduce the final variation in the barn.

Another approach to increasing weight gain of the lighter pigs in a group is to bump amino acid levels. In reality, the lightest pigs may not actually have a higher amino acid requirement than the heavier pigs. Weight does not accurately depict the amino acid requirements within a population.

Rate of protein accretion and feed intake are the major determinants of amino acid requirements. Therefore, the heavier, faster-growing pigs may actually have a higher amino acid requirement because they have higher protein deposition rates, even though they consume more feed. With current knowledge, we formulate diets for the light and heavy groups to have similar amino acid:calorie ratios based on their average weight.

The use of alternative feed ingredients that are cheaper than corn or soybean meal can lower diet costs. The challenge is to balance the lower cost with any other potential pitfalls that may come with the alternative ingredients.

Before any alternative ingredient is used, the nutrient composition must be understood, and the aid of a professional nutritionist should be sought to minimize any negative effects and to capture the potential value.

For example, the use of distiller's dried grains with solubles (DDGS) will lower diet cost in most situations. However, use of the ethanol by-product also reduces carcass yield, and has been shown to increase the variation in weight within a common group of pigs when fed through marketing.

While less data is available on the effects of various bakery by-products, meat and bonemeal or fibrous ingredients, such as wheat middlings or soybean hulls, on variation of pig weight, producers need to be aware of the potential lost revenue if the alternative ingredients result in increased variation due to changes in feed intake patterns.

In addition, the economic impact of the change in carcass yield or quality (carcass fat softness) must be taken into account when determining the value of alternative feed ingredients. With any alternative, increased sampling and ingredient testing must occur to determine nutrient variability. Then, an informed decision can be made relative to any potential negative impacts that the variability will have on pig performance.

Although “high-health systems” is a nebulous term, it is meant to encompass the many factors that improve the health status of pigs within a group.

Research has shown that pigs reared in an all-in, all-out manner have less variation in growth rate and market weight (7.5% vs. 8.8% CV) than pigs reared in a continuous-flow manner.

Other system design factors that can lead to sustained improvements in health status, such as reduction in sources of pigs, location of the source herd and location of the growing barns, would be expected to also reduce variation in weight gain.

Promptly treating clinical disease to enhance recovery and reduce spread of the bacteria within the group will reduce the number of lightweight pigs at market and, thus, reduce variation.

The use of feed-grade antibiotics has been cited as a means of reducing variation in final market weight. Published evidence is lacking that this phenomena actually occurs because the impact is relatively small. A large number of pigs or groups of pigs are required to experimentally prove or disprove the concept.

However, there is evidence that in multi-site production systems, feeding antibiotics consistently results in improved growth rate of nursery pigs, but not in finishing pigs.