PREDICTING THE EFFECTS OF ANIMAL VARIATION ON GROWTH AND FOOD-INTAKE IN GROWING PIGS USING SIMULATION MODELING

All pig nutrition models to date predict growth responses of either an individual animal or the average animal of a given population over ti me. Translating the predicted nutrient requirements from the average a nimal to the population introduces a number of errors as the cause-and -effect response of the average animal is different from the populatio n response. To overcome the problem of estimating the requirements for a given population using models it is necessary to simulate a number of individuals representative of a population and then average these r esults. This approach however, requires a knowledge of those animal ch aracteristics that vary between individuals and the nature of their di stribution. In this paper a scaled growth rate constant (B), protein weight at maturity (Pm) and the ratio of lipid to protein at maturity (LPRm) are the parameters used to define an individual animal. As no d ata existed from which the nature of the distribution of B, Pm and LP Rm can be estimated for pigs of different strains and sexes, and due t o the impracticality of determining this variability by experimentatio n, a simulation model was used to estimate the variations within each parameter. In addition this payer quantifies the subsequent effects th ese distributions have on the generic variability of average daily gai ns (ADG) and daily food intake (FI) over a live-weight range of 25 to 90 kg. Comparisons were made between the genetic variation determined by modelling and those published in the literature. The results indica ted coefficients of variation for B Pin and LPRm of 0.01, 0.05 and 0. 10, respectively An increase in the variability of all three parameter s resulted ill an increase in the variation in ADG whilst only an incr ease in the variation of B and LPRm affected the distribution of FI.