Genetic and Nutritional Effects on Carcass Chemical Composition and Organ Weights of Market Swine

Half-carcasses of 128 market swine were analyzed for moisture, ether extract (EE), protein and ash. The longissimus muscles were analyzed for EE and some organ weights were measured. A balanced 25 of treatments included shire (Y) breeds, high (H) and low (L) backfat lines within each breed, sex (female and castrated male) and two levels each of dietary protein (20 and 14%) and energy (3.6 and 3.2 kcal ME/g). Each of the breed-line groups differed significantly from each other in carcass chemical composition ranging from the highest protein and lowest EE in YL through DL, YH to DH which had the lowest protein and highest EE. Males were significantly lower in protein and higher in EE than females. A breed-line × sex interaction (P<.01) for all components except ash showed that the greatest difference between sexes was in the L lines. Carcasses from pigs fed the 20% protein diet were higher in moisture and lower in EE (P<.05) than those of pigs fed the 14% diet. No other diet effects and no interaction of diet with breed-line variables were significant. The EE of the longissimus muscle was significantly lower in YL and higher in DH than in the other breed-line groups and higher (P<.01) in males than in females. Differences in organ weights (liver, heart, kidney, stomach) among the breed-line groups were significant and the liver and kidneys of pigs fed the 20% protein diet were heavier (P<.01) than those from pigs fed the 14% diet.