Nutritional programs can certainly play a major role in the amount of weight variation within a common group of pigs. The ability to minimize this variation involves many management, nutritional and health decisions.

From a nutritional standpoint, there are numerous ways to minimize the variation within a common group of pigs by providing consistent, nutritionally adequate diets formulated for specific genders and weights. Historically, this has been accomplished by feeding simple cereal grain-soybean meal-based diets throughout the various production stages.

However, with current feed ingredient prices at record highs, any and all options to determine optimum use of alternative ingredients, as well as the most economical nutrient levels of various diets, are being explored.

As feed alternatives or lower-quality (less digestible) replacements for lactose, protein and energy are utilized in diets, the potential for increased variation in a common pig group is more likely.

The effect of increased variation generally is not evaluated when diet decisions are made. The decision to lower feed cost is commonly the overriding factor.

While limited research data has evaluated the impacts of different alternatives and lower-quality ingredients on total group weight variation, the effects can be pronounced if feed ingredients are of poor quality.

It is important to remember that increasing the growth rate of the entire group of pigs will not reduce variation in the group or the need to sort pigs at market. Increasing growth rate will, however, increase the weight of the slow-growing pigs, which is the main marketing issue.

Following are eight areas that producers should focus on as they attempt to increase the growth rate of an entire group of pigs:

1. Use genetics capable of high growth rate in commercial conditions.

2. Maintain high health status.

3. Identify and use sows with high milk production.

4. Aim for high lactation feed intake to increase weaning weight.

5. Increase age at weaning.

6. Increase energy density of the diet to increase growth rate.

7. Feed correct amino acid levels.

8. Optimize feeding of ractopamine (Paylean from Elanco Animal Health).

While this list provides a basis for improving the growth rate of an entire group, following are several areas where nutrition may have direct implications on reducing actual variation within a group of pigs.

• Improve pig birth and weaning weights.

  Total pigs born/litter and number born alive/litter have increased dramatically in the last several years. Since 2000, the rate of progress has been approximately 0.2 pigs/litter each year.

  This dramatic increase in litter size has been achieved through the application of genetic improvement focusing on ovulation rate. While genetic selection for increased ovulation rate has increased litter size, unfortunately, it has also increased the number of stillborns/litter and lowered average pig birth weights.

  Many factors affect fetal growth and development, including sow ovulation rate, uterine capacity, genotype, nutrition and feeding regimens.

  Researchers are beginning to understand that uterine capacity, which determines the number of fetuses maintained during pregnancy, is one of the greatest limitations to litter size. And litter weight is directly related to litter size. Pigs born in large litters are lighter at term because of the decreased placental surface area available to each.

  Additionally, mobilization of energy substrates increases in sows with larger litters. Glucose is a major energy substrate for fetuses, and has been shown to decrease in sows with large litters, due to the high-energy requirement necessary to sustain the uterus and fetuses.