Greenwood P L, Hunt A S, Hermanson J W, Bell A W
Department of Animal Science, Cornell University, Ithaca, New York 14853-4801, USA.
J Anim Sci. 2000 Jan;78(1):50-61. doi: 10.2527/2000.78150x.
This study investigated effects of birth weight and postnatal nutrition on growth and development of skeletal muscles in neonatal lambs. 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) lambs 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 lambs was 43% that in H lambs; aggregate weights of ST and seven other dissected muscles were similarly reduced. In ST muscle of L lambs, mass of DNA, RNA, and protein were also significantly reduced to levels 67, 60, and 34%, respectively, of those in H lambs. However, myofiber numbers of ST, tibialis caudalis, or soleus muscles did not differ between the L and H birth weight lambs and did not change during postnatal growth. During postnatal rearing, daily accretion rate of dissected muscle was lower in L than in H lambs. Accretion of muscle per kilogram of gain in empty body weight (EBW) was reduced in the slowly grown L lambs compared with their H counterparts, although the difference was less pronounced between the rapidly grown L and H lambs. Throughout the postnatal growth period, ST muscle of L lambs contained less DNA with a higher protein:DNA ratio at any given muscle weight than that of H lambs. Slowly grown lambs had heavier muscles at any given EBW than rapidly grown lambs. Content of DNA and protein:DNA ratio in ST muscle were unaffected by postnatal nutrition, but RNA content and RNA:DNA were greater and protein:RNA was lower at any given muscle weight in rapidly grown lambs. Results suggest that myofiber number in fetal sheep muscles is established before the presumed, negative effects of inadequate fetal nutrient supply on skeletal muscle growth and development become apparent. However, proliferation of myonuclei may be influenced by fetal nutrition in late pregnancy. Reduced myonuclei number in severely growth-retarded newborn lambs may limit the capacity for postnatal growth of skeletal muscles.
本研究调查了出生体重和出生后营养对新生羔羊骨骼肌生长发育的影响。低出生体重（L组；平均±标准差2.289±0.341千克，n = 28）和高出生体重（H组；4.840±0.446千克，n = 20）的雄性萨福克×（芬兰羊×多塞特羊）羔羊，从出生到体重（LW）达到约20千克，分别采用液体日粮单独饲养，使其快速生长（自由采食，平均日增重337克，n = 20）或缓慢生长（平均日增重150克，n = 20）。出生时，L组羔羊的半腱肌（ST）重量为H组羔羊的43%；ST肌和其他七块解剖肌肉的总重量也有类似程度的降低。在L组羔羊的ST肌中，DNA、RNA和蛋白质的含量也显著降低，分别降至H组羔羊的67%、60%和34%。然而，L组和H组出生体重羔羊的ST肌、尾侧胫骨肌或比目鱼肌的肌纤维数量并无差异，且在出生后生长过程中也未发生变化。在出生后饲养期间，L组羔羊解剖肌肉的日生长率低于H组羔羊。与H组羔羊相比，生长缓慢的L组羔羊每千克空腹体重增加量（EBW）的肌肉生长量减少，尽管生长快速的L组和H组羔羊之间的差异不太明显。在整个出生后生长期间，在任何给定的肌肉重量下，L组羔羊的ST肌所含DNA较少，蛋白质:DNA比值高于H组羔羊。在任何给定的EBW下，生长缓慢的羔羊肌肉比生长快速的羔羊更重。ST肌中的DNA含量和蛋白质:DNA比值不受出生后营养的影响，但在任何给定的肌肉重量下，生长快速的羔羊的RNA含量和RNA:DNA比值更高，蛋白质:RNA比值更低。结果表明，在胎儿营养供应不足对骨骼肌生长发育产生的假定负面影响显现之前，胎羊肌肉中的肌纤维数量就已确定。然而，肌核的增殖可能在妊娠后期受胎儿营养的影响。严重生长迟缓的新生羔羊肌核数量减少，可能会限制出生后骨骼肌的生长能力。
