Genetic and Environmental Effects and Interactions in Swine Growth and Feed Utilization

Direct and interaction effects of breed, line, sex, diet protein and energy levels on swine growth and feed conversion were investigated in a 25factorial arrangement of treatments. Each of the 32 subclasses consisted of two pens, each with two pigs. The 128 pigs were placed on test at 9 weeks of age and taken off test for slaughter at 100 kilograms.Barrows and gilts of lines previously selected for up to 17 generations for either thicker or thinner backfat in Durocs and Yorkshires were fed diets with 20 or 14% protein and either 3.60 or 3.20 kcal of M.E./g. Average air temperature and water evaporation rates were recorded.Durocs outgained Yorkshires. High-fat lines ate more feed than low-fat lines. Low-fat Durocs outgained high-fat Durocs, but the reverse was true for Yorkshires, resulting in an interaction of breed with line for gain. Barrows gained 7% faster (P< .01) and consumed 6% more feed (P< .01) than gilts.