Cellular Growth of Skeletal Muscle in Swine Differing in Muscularity

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Abstract
Skeletal muscle growth of swine differing in muscularity was studied by analysis of DNA, RNA and protein in the biceps femoris muscle of "light muscled" (LM) and "heavy muscled" (HM) Duroc pigs. Three HM litters and 3 LM litters were produced by mating HM gilts to HM boars and LM gilts to LM boars, respectively. Boars and gilts were selected based on visual appraisal and on carcass data of littermate barrows and gilts. One pig from each litter was slaughtered at 1,15, 30, 62, 105, 145 and 210 days of age (42 pigs total). Growth rate did not differ among HM and LM pigs. HM pigs had less backfat, larger loin eye areas and greater semitendinosus and biceps femoris weights. These differences were accentuated later in the growth period. DNA and RNA concentrations in the biceps femoris muscle decreased significantly with age (P < .01) but there were no significant differences between groups. Protein concentrations increased between 1 and 30 days but declined between 30 and 210 days of age and were slightly higher in HM pigs. Total DNA, RNA, and protein in the biceps femoris muscle increased with age (P < .01). Total DNA and total protein was greater in the HM pigs when differences over all age groups were analyzed (P < .05) but group differences were not significant for total RNA even though the HM pigs had higher total RNA. RNA to DNA and protein to DNA ratios tended to increase with age indicating hypertrophic growth. RNA to DNA and protein to DNA ratios were significantly different between HM and LM pigs in a few age groups but no regular pattern of differences was present. It was concluded that the greater biceps femoris muscle mass in HM pigs was accompanied by a proportional increase in the number of nuclei present in the muscle since protein to DNA ratios were similar between the two groups of animals. Copyright © 1975. American Society of Animal Science . Copyright 1975 by American Society of Animal Science.

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