Swine

Pig Body Weight Variation

Young Animal : Management

Dan McManus

DVM - Young Animal Swine Specialist

Pig body weight variation is a serious problem that is often overlooked until pigs are ready to go to market.

Variation then becomes an urgent and significant management problem as pigs require sorting and remixing, and light weight culls are removed to another site so that facilities can be washed and prepared for the next group. 

Pig body weight variation doesn’t just happen in the finisher. Variation magnifies itself throughout the life of the pigs, and becomes greater as pigs age. For example, at weaning, the average weight of a group of pigs may be 13 pounds with a range of body weights from 8-to-18 pounds. This is a 10 pound spread. By the end of the nursery period, the average weight of this group of pigs may be 66 pounds with a range of body weights from 46-to-86 pounds. The range of variation has now increased to 40 pounds. By the time the group of pigs approach market weight, the variation in pig body weight from the lightest to the heaviest may be 100 pounds or more.

What is an acceptable amount of variation? Data from the Prairie Swine Centre in Canada supports the following recommendations1. For pigs at weaning, the Coefficient of Variation (CV) should be 20 percent or less. For an accurate estimation, at least 100 randomly selected pigs need to be weighed individually. For pigs coming out of the nursery, the CV should be 15 percent or less. For an accurate estimation, at least 50 randomly selected pigs need to be weighed individually. For pigs at market weight, the CV should be 10 percent or less. For an accurate estimation, at least 50 randomly selected pigs need to be weighted individually before the first group of pigs leaves the facility for market. 

Pig body weight variation can be reduced. Management practices and products that reduce variation early in a pig’s growth phase provide the biggest benefits. Feeding UltraCare® Gel to all pigs as they enter the nursery reduces pig variation as shown by several studies conducted at the Purina Animal Nutrition Research Center (Figures 1 and 2). At the end of the nursery period, small pigs not offered gel had a CV for weight of 23.4 percent while pigs fed gel had a CV for weight of only 21 percent, indicating a more uniform group. Gel not only reduced pig weaning weight variation in smaller pigs, but also shifted the nursery end weight distribution to the right in older, heavier pigs (Figure 2) receiving gel leading to heavier, more uniform pigs going to the finisher. 
Figures displaying body weight for pigs

Begin with the end in mind. To reduce pig weight variation at marketing time, feed UltraCare® Gel to all pigs as they enter the nursery.
 
1Patience et all, 2003. Prairie Swine Centre Annual Research Report 2003 pp. 36