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Effect of Selection for Backfat Thickness in Swine on Fetal Skeletal Muscle Metabolism¹

University of Georgia, Athens 30602 and and US Department of Agriculture^,3,4,, Athens, GA 30613

Abstract

At 110 d of gestation, fetuses were removed from sows selected for high (obese) or for low (lean) backfat thickness. The body weights of lean (1,031 ± 64 g) and obese (864 ± 55 g) fetuses were not significantly different. Analysis of muscle composition and of in vitro metabolic characteristics was conducted on the biceps femoris muscle. The percentage of dry weight, protein and glycogen was greater in the muscle of obese fetuses than in the muscle of lean fetuses (P<.01, P<.05, and P<.05, respectively). Percentage of muscle triglyceride was similar (P>.05) between the two phenotypes. The rate of glucose oxidation to C0₂ tended to be greater (P<.07) and the rate of lactate production was lower (P<.05) in the muscle from obese fetuses than in the muscle from lean fetuses. The rates of leucine oxidation to CO₂ and of palmitate oxidation to CO₂ did not differ between phenotypes. The rate of -ketoisocaproate release from the muscle of obese fetuses was greater (P<.05) than from that of the lean fetuses. The rate of release of alanine and of glutamine plus glutamate did not differ between phenotypes. The rate of esterification of palmitate did not differ between phenotypes. It was concluded that abnormalities in glucose metabolism and in the partitioning of leucine between oxidation and release as the keto acid existed at 110 d of gestation in the muscle of obese fetuses. Any relation between these differences and ultimate differences in carcass composition were not evident.

¹ The authors thank Dr. R. W. Seerley, Dept. of Anim. Sci., Univ. of Georgia and the personnel of the Univ. of Georgia Swine Farm for providing animal facilities and for maintaining the animals used in this study.

² Dept. of Foods and Nutr.

³ Richard B. Russell Agricultural Res. Center, ARS.

⁴ Mention of a trade name, proprietary product, or specific equipment does not constitute a guarantee or warranty by the U.S. Dept. of Agriculture and the Univ. of Georgia and does not imply its approval to the exclusion of other products which may be suitable.