Comparison of Fat and Muscle Development in Pietrain and Large White Piglets

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Abstract
Large White and Pietrain piglets ranging in age from birth to 28 days were compared for fat and muscle development. As expected, fatness and muscle weight increased (P<.01) with age. Shoulder backfat, did not differ between breeds, however, there was a significant (P<.03) breed × age interaction for loin backfat with the Large Whites having the most backfat at the older ages. Both lipid and water content of the subcutaneous fat varied by age (P<.01) and breed (P<.06), respectively. At 14 days the outer and inner fat layers were clearly delineated in both breeds. The outer subcutaneous fatty tissue of the Large White piglets appeared to be more mature at birth than that of the Pietrain breed as evidenced by the large aggregation of fat cells and the greater rate at which the fat cells subsequently filled the whole tissue. In both breeds it was clear that the deposition of shoulder fat which occurred between birth and 28 days could not have been accounted for by the observed change in mean diameter of the population of cells detectable at birth. A slight but nonsignificant increase in muscle weight as well as an increase in rate of muscle growth occurred in Pietrain piglets. The lipid increase in the longissimus muscle was also similar between breeds with the biggest increase occurring at 3 days. Histological evidence indicated that this increase in intramuscular lipid was the result of an accumulation of intrafiber lipid droplets in the muscle from birth to 3 days rather than an increase in interfascicular fat. Muscle fiber differentiation was evident in the longissimus muscle at 7 days and essentially complete at 14 days. Significant changes in fatty acids were observed over the whole period. Breed means revealed a difference in palmitoleic acid obtained from the total lipid fraction as well as a difference in stearic and linoleic acids from the phospholipid fraction of the longissimus muscle. In addition, palmitoleic and stearic acids, of the neutral lipid portion were significantly different (P<.01) between breeds. Copyright © 1978. American Society of Animal Science . Copyright 1978 by American Society of Animal Science.