Effects of Protein, Breed Cross, Sex and Slaughter Weight on Swine Performance and Carcass Traits

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Abstract
Two-hundred and eighty-eight crossbred pigs were evaluated for the effects of sex, breed cross, dietary protein level and slaughter weight and their first-order interactions on performance and carcass traits. Barrows grew faster than gilts but had lower percentages of ham and loin, smaller loin eyes, shorter carcasses, more backfat (P<.01) and increased marbling (P<.05). Lean cross (L-cross) pigs had higher average daily gains, lower marbling and color scores, less backfat, longer carcasses, larger loin-eye areas and higher ham and loin percentages (P<.01) than did average pigs (A-cross). Compared to a 12% protein diet, a 16% diet decreased marbling scores and improved feed efficiency (P<.01). Pigs slaughtered at 113.5 kg live weight grew faster (P<.01) and less efficiently overall than did pigs slaughtered at 98.5 kilograms. The heavy slaughter-weight group produced carcasses with less ham and loin percentages, larger loineye area and increased carcass length, backfat and dressing percentage (P<.01). Although the L-cross pigs grew more efficiently on the 16% protein diet than on the 12% diet, the A-cross pigs did not, resulting in a significant cross × protein interaction for feed efficiency. This interaction was not significant for any other traits. This study provides no evidence that gilts respond differently than barrows to high protein diets and therefore suggests that feeding barrows and gilts separately is not warranted. However, providing leaner strains of pigs a higher protein diet seems justified because it may improve feed conversion. Copyright © 1980. American Society of Animal Science . Copyright 1980 by American Society of Animal Science.