Economic values of traits for pig improvement. I. A simulation model

Abstract

A computer model simulating life cycle production of a breeding sow and growth performance of her offspring was developed to estimate economic values of reproduction and growth performance traits. A biological growth model, simulating the digestion and metabolism of dietary nitrogen in growing pigs (20 to 85 kg), was part of the life cycle model. The growth model was based on the linear/plateau relationship between daily protein deposition and digestible energy intake. A farrow-to-finish production system, with slaughter pigs marketed at fixed liveweights, was simulated. Input variables were: gilt age at first oestrus, weaning to oestrus interval, number of pigs born alive per litter, and pre-weaning mortality for each parity. Economic inputs included prices of feed ingredients, carcass returns and non-feed costs. The upper limit to body protein deposition rate, mean daily ad libitum digestible energy intake and minimum lipid to protein deposition ratio were assumed the major genetic determinants of pig growth. The model output included average daily gain, ad libitum daily feed intake, backfat thickness, and life cycle reproductive performance and profit. The combined life cycle profit was expressed in the form of an Annualized Present Value. Life cycle profit was calculated for a range of simulated pig genotypes.