Simulation of Heterosis Effects on Costs of Pork Production

Individual plus maternal heterotic effects on swine production were simulated with a bio-economic model by changing performance levels of eight traits:. –8 d in age at puberty, +3% in conception rate, +.94 in pigs born/litter, +.035 kg in pig birth weight, +2.05 Mcal·sow-1·d-1 in maximum milk output, +8% in preweaning survival, +10.8% in protein growth rate and +17.3% in fat growth rate. Associated heterosis simulated for other traits, such as weaning weights and postweaning gain/feed, was similar to experimental results. Effects of heterosis on biological (feed Mcal/kg) and economic ($/kg) costs were evaluated by simulating two- and three-breed crosses and purebred production. Pig heterosis reduced $/kg lean or $/kg live weight by 4% for marketing at 100 kg, and by 6% for $/kg of lean and 8% for $/kg of live weight for marketing at average 185-d weight. Sow heterosis reduced $/kg lean or $/kg live weight about 4%. Pig heterosis reduced feed Mcal/kg by only 1% and Mcal/kg live weight by 3%, and both were reduced only 1% by maternal heterosis. Traits that reduced litter costs/kg of output by increasing output/litter were responsible for most effects of heterosis on $/kg. However, heterosis in growth rate was important for feed Mcal/kg of lean marketed at 100 kg, and for feed Mcal/kg of live weight marketed at either 100 kg or at 185-d weight. Nonfeed costs/kg lean or live weight marketed at 100 kg were reduced more than feed costs by pig heterosis (–5 or –6 vs –2 or –3%) and by sow heterosis (–8 vs –1 or –2%). Effects of pig heterosis on nonfeed costs were increased to –12 or –14% by marketing at mean 185-d weight. Percentage reductions in total costs from heterosis were about one-third as large as corresponding increases in output/litter at market age.