A GROWTH-MODEL TO ESTIMATE ECONOMIC VALUES FOR FOOD-INTAKE CAPACITY IN PIGS

A biological growth model was developed to study economic values for average ad libitum food intake capacity (FIC) in growing pigs. The model was based on the linear/plateau relationship between protein deposition and food intake. Input variables were: minimum fat to protein deposition ratio (R), maximum protein deposition rate (Pd(max)) and food intake (FI). Output variables were production traits and production costs. Economic values (under commercial conditions with ad libitum feeding) were derived with the growth model for each of the traits FIC, R, and Pd(max) keeping the other two traits constant, for three alternative levels of FIC. If FIC was too low to realize Pd(max), FIC had a positive economic value, R had a negative economic value and the value of Pd(max) was zero. If FIC was higher than necessary to realize Pd(max), economic values were negative, zero and positive for FIC, R, and Pd(max) respectively. If FIC was just sufficient to realise Pd(max), the lowest production costs occurred. Now, R had a negative economic value and Pd(max) had a positive economic value. With a restricted feeding regimen under commercial conditions a daily food supply just sufficient to realize Pd(max) should be pursued. It was concluded that use of a biological growth model to estimate economic values for FIC would give more insight into correct selection strategies than would the use of an economic model.