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. 1998 Sep;76(9):2354-67. doi: 10.2527/1998.7692354x.
We investigated the effects of birth weight and postnatal nutrition on growth characteristics of neonatal lambs. Low- and high-birth-weight male lambs were individually reared on a high-quality liquid diet to grow rapidly (ad libitum access to feed) or slowly (ADG 150 g) to various weights up to 20 kg live weight (LW). Average daily gain tended to be greater in the high- (mean+/-SE 345+/-14 g) than in the low- (329+/-15 g) birth-weight lambs given ad libitum access to feed owing to slower growth by the small newborns during the immediate postpartum period. At birth, on a weight-specific basis, small newborns contained 6.4% less nitrogen and tended to have more ash (8.9%) than the high-birth-weight newborns. Daily rates of fat, ash, and GE accretion were greater, and nitrogen accretion tended to be greater in the rapidly grown large newborns than in their small counterparts. At any given empty body weight (EBW) during rearing, low-birth-weight lambs contained more fat and less ash, resulting in slowly and rapidly grown small newborns containing 39.3 and 42.7 Mcal GE, respectively, at completion of the study (17.5 kg EBW), compared with 34.8 and 40.5 Mcal in their large counterparts. The differences in fatness and energy content between the birth weight categories are attributed to energy requirements for maintenance that were approximately 30% lower, coupled with higher relative intakes in the low-birthweight lambs, during the early postnatal period. At this time, the ability to consume nutrients in excess of lean tissue growth requirements was apparently more pronounced in small than in large newborns, which resulted in lower efficiency of energy utilization for tissue deposition. Furthermore, body composition differences between the slowly and rapidly reared lambs support the notion of a priority of lean tissue over fat when nutrient supply is limited.
我们研究了出生体重和产后营养对新生羔羊生长特性的影响。将低出生体重和高出生体重的雄性羔羊分别用高质量液体日粮单独饲养，使其快速生长（自由采食）或缓慢生长（平均日增重150克），直至达到20千克活重的不同体重。自由采食的情况下，高出生体重羔羊（平均±标准误 345±14克）的平均日增重往往高于低出生体重羔羊（329±15克），这是因为小新生羔羊在产后早期生长较慢。出生时，按体重比计算，小新生羔羊的氮含量比高出生体重新生羔羊少6.4%，且灰分含量往往更高（8.9%）。快速生长的大新生羔羊的脂肪、灰分和总能沉积的日速率更高，氮沉积也往往高于其小体重的同类羔羊。在饲养过程中的任何给定空腹体重（EBW）下，低出生体重羔羊的脂肪含量更高，灰分含量更低，因此在研究结束时（17.5千克EBW），缓慢生长和快速生长的小新生羔羊的总能分别为39.3和42.7兆卡，而其大体重同类羔羊分别为34.8和40.5兆卡。出生体重类别之间的脂肪含量和能量含量差异归因于产后早期维持能量需求约低30%，同时低出生体重羔羊的相对摄入量更高。此时，小新生羔羊显然比大新生羔羊更能摄入超过瘦组织生长需求的营养物质，这导致组织沉积的能量利用效率较低。此外，缓慢饲养和快速饲养的羔羊之间的身体组成差异支持了在营养供应有限时瘦组织优先于脂肪的观点。
