Influence of weaning age and nursery diet complexity on growth performance and carcass characteristics and composition of high-health status pigs from weaning to 109 kilograms.

We examined the influence of weaning age (9 or 19 +/- 1 d) and nursery diet complexity on growth performance and carcass composition of 192 high-health status barrows from weaning to 109 kg. Pigs were fed diets of different complexity (high, medium, or low) in various regimens from weaning to 18.7 kg. They then were fed common corn-soybean meal-based diets from 18.7 to 109 kg. Increasing diet complexity improved ADG from weaning to 7.0 kg (P < .10) but had no effect (P > .10) from 7.0 to 18.7 kg. Thus, increasing diet complexity seems to improve ADG only in the early period after weaning. Age at 109 kg was similar (P > .10) for the pigs weaned at 9 and 19 d. However, pigs fed the medium-complexity regimens were the youngest (P < .01) at 109 kg. Interactions (P < .06) were observed for carcass lipid and lipid:protein accretion from 18.7 to 109 kg. These were the result of pigs weaned at 9 d of age having higher carcass lipid and lipid:CP accretion rates when fed the low-complexity regimens than when fed the medium- or high-complexity regimens. However, pigs weaned at 19 d of age had similar carcass lipid and lipid:protein accretion ratios regardless of diet complexity. When health status was similar, growth performance was similar between weaning ages but was influenced by diet complexity. Carcass lipid and lipid:protein deposition ratios increased when simple regimens were fed to pigs weaned at 9 d of age in the subsequent growing-finishing period.