Herd Health and Management
Measuring Variation In Performance
The cost of variation in performance takes on increased attention and importance as hog barns become larger and more sophisticated in both design and management.
The use of all-in, all-out production systems magnifies the impact of variation because space utilization becomes more obvious.
A trio of Prairie Swine Centre researchers outlined the parameters of variation and methods for change.
Variation is most commonly measured two ways — standard deviation (SD) and coefficient of variation (CV). SD refers to the weight dispersion of pigs. In a normal distribution, one SD above the mean will capture 68.27% of the pigs in the group.
Dividing the SD by the mean and multiplying it by 100 determines the CV. Table 1 describes the statistics from groups of pigs at three different ages. The CVs in Table 1 would be typical of a well-managed herd.
Figure 1 provides an example of a bell curve of pig weights at 20 weeks of age.
Two categories encompass most causes of variation: genetics and environment. Ideally, environmental factors are removed so the pig can fully express its genotype. In reality, however, this becomes very difficult. Environmental factors affecting variation include feed and water, exposure to pathogens and behavioral challenges.
There are a number of management steps that pork producers can take to overcome variation problems in hog barns. To have an impact on variation, CV must usually be larger than 15%.
Segregating production has the most impact. Segregating barrows and gilts is suggested because barrows eat more feed than gilts, and therefore tend to reach market weight five to seven days sooner than gilts.
Another form of segregation involves separating a group of hogs by size. Take the smallest 10-15% of the pigs at weaning, or when they exit the nursery, and either place them in a separate barn or sell them outright. Or split large groups in two, into heavy and light groups of pigs.
Researchers: J.F. Patience, A.D. Beaulieu and H.W. Gonyou, Prairie Swine Center, Saskatchewan, Canada. Contact Patience by phone at (306) 373-9922 or fax (306) 955-2510.