INFLUENCE OF DIETARY NUTRIENT DENSITY, LEVEL OF FEED INTAKE AND WEANING AGE ON YOUNG PIGS. I. PERFORMANCE AND BODY COMPOSITION

Abstract

The performance and final body composition of 128 pigs weaned at either 3 or 4 wk of age and receiving either a normal density (ND) or high density (HD) diet ad libitum or restricted (85% of ad libitum) was determined over a 28-d period. Pigs weaned at 4 wk consumed more feed (P < 0.001) and grew faster (P < 0.005) than those weaned at 3 wk, but body weights at a similar age were not different. The HD diet supported greater gains (P < 0.01) and gain to feed (G:F) ratio (P < 0.005) than the ND diet. Restricting feed intake reduced gains (P < 0.001) and improved G:F ratio (P < 0.05). Interaction effects showed that performance of pigs weaned at 4 wk was less affected by nutrient density and feed restriction than that of pigs weaned at 3 wk of age. Pigs weaned at 4 wk had heavier carcasses at the end of the 28-d period than those weaned at 3 wk but there was no difference in percent water, fat or protein. Nutrient density did not affect body composition. However, restricted feeding increased percent water (P < 0.05), reduced percent fat (P < 0.05) and increased percent protein on a dry matter basis (P < 0.02). A significant interaction between weaning age and level of feed intake showed that restricting the intake of pigs weaned at 4 wk reduced fat deposition more than when intake was restricted for pigs weaned at 3 wk of age (P < 0.05). An interaction between diet, intake level and sex (P < 0.01) showed that even in young pigs, barrows tend to fatten more than gilts when energy intake is adequate and less when energy intake is restricted. Key words: Pigs, weaning, nutrient density, body composition, performance