Alternative Nonlinear Mixed Effects Models for Swine Growth

Purdue University 2002 Swine Research Report. The production of pigs has developed towards highly specialized coordinated production systems. Variability in the growth rates of pigs is important to the economic costs and returns of both the pork producer and processor. The optimization of pork production systems including the evaluation of alternative management and marketing strategies requires knowledge of the variation in body weight and carcass composition. Typically, pigs are weighed every 14-21 days from 50 lbs to 250 lbs live weight to develop live weight growth curves. Heavier pigs at weaning usually have a competitive advantage and remain heavier than the other pigs of the group, all the way to market. Also, the variation among the pigs for live weight increases as age increases. The objective of this study was to evaluate alternative mixed effects models of a standard growth function.