摘要：

This study investigated effects of birth weight and postnatal nutrition on growth and of skeletal muscles in neonatal . Low (L; mean +/- SD 2.289 +/-.341 kg, n = 28) and high (H; 4.840 +/-.446 kg, n = 20) birth weight male Suffolk x (Finnsheep x Dorset) were individually reared on a liquid diet to grow rapidly (ad libitum fed, ADG 337 g, n = 20) or slowly (ADG 150 g, n = 20) from birth to live weights (LW) up to approximately 20 kg. At birth, weight of semitendinosus (ST) muscle in L was 43% that in H ; aggregate weights of ST and seven other dissected muscles were similarly reduced. In ST muscle of L , mass of DNA, , and protein were also significantly reduced to levels 67, 60, and 34%, respectively, of those in H . However, myofiber numbers of ST, tibialis caudalis, or soleus muscles did not differ between the L and H birth weight and did not change during postnatal growth. During postnatal rearing, daily accretion rate of dissected muscle was lower in L than in H . Accretion of muscle per kilogram of gain in empty body weight (EBW) was reduced in the slowly grown L compared with their H counterparts, although the difference was less pronounced between the rapidly grown L and H . Throughout the postnatal growth period, ST muscle of L contained less DNA with a higher protein:DNA ratio at any given muscle weight than that of H . Slowly grown had heavier muscles at any given EBW than rapidly grown . Content of DNA and protein:DNA ratio in ST muscle were unaffected by postnatal nutrition, but content and :DNA were greater and protein:was lower at any given muscle weight in rapidly grown . Results suggest that myofiber number in fetal muscles is established before the presumed, negative effects of inadequate fetal nutrient supply on skeletal muscle growth and become apparent. However, proliferation of myonuclei may be influenced by fetal nutrition in late . Reduced myonuclei number in severely growth-retarded newborn may limit the capacity for postnatal growth of skeletal muscles.

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