Index Selection and Feed Intake Restriction in Swine. I. Effect on Rate and Composition of Growth

Abstract

Summary The objectives of this experiment were to determine the effects of index selection for increased average daily gain and decreased backfat, and the effects of restriction of daily feed intake, on rate and composition of growth in swine. A total of 53 barrows from select and control lines were randomly assigned to three feeding levels at 83 d of age, and 33 littermate barrows were slaughtered to establish initial body composition. The trial was approximately 105 d and the feeding levels were twice daily to appetite (AP), once daily feeding of 91% of appetite (APgl) and once daily feeding of 82% of appetite (AP82). At slaughter, all pigs were dissected and analyzed for chemical composition. Average daily gain was higher (P<.01) while backfat was lower (P<.001) for select than for control pigs. Restriction of feed intake reduced (P<.01) growth rate. Even at heavier final weights, select pigs had a greater (P<.O01) proportion of lean than control pigs. Pigs fed the APgl and AP82 levels of intake had a greater (P<.01) proportion of lean than pigs fed the AP level. Daily gains of protein, water and lean were higher (P<.01) for select than for control pigs. However, daily fat gain was lower (P<.05) for select pigs. Restricting feed intake reduced (P<.05) daily fat gain, but daily gains of protein, water and lean were similar for pigs on the AP and AP91 levels. However, daily gains of protein, water and lean were lower for