Greenwood P L, Hunt A S, Slepetis R M, Finnerty K D, Alston C, Beermann D H, Bell A W
Department of Animal Science, Cornell University, Ithaca, New York 14853-4801, USA.
J Anim Sci. 2002 Nov;80(11):2850-61. doi: 10.2527/2002.80112850x.
This study investigated effects of birth weight and postnatal nutrition on regulation of energy metabolism in the neonatal lamb. Low (mean +/- SD 2.289 +/- 0.341 kg, n = 28) and high (4.840 +/- 0.446 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, small newborns had higher plasma concentrations of urea nitrogen (mean +/- SEM 8.31 +/- 0.25 vs 6.39 +/- 0.32 mM, P = 0.002) and somatotropin (ST, 49.1 +/- 17.0 vs 10.8 +/- 4.3 ng/mL, P = .045) and lower IGF-I (36.1 +/- 6.8 vs 157.7 +/- 21.8 ng/mL, P < 0.001) than large newborns. Plasma glucose (1.42 +/- 0.23 vs 2.63 +/- 0.95 mM, P = 0.147) and insulin (0.09 +/- 0.02 vs 0.13 +/- 0.06 ng/mL, P = 0.264) concentrations did not differ. Urea nitrogen concentration in plasma peaked and then declined rapidly in all lambs during the first week postpartum, and plasma ST declined on a body-weight-related basis from birth. During rearing to 20 kg LW, plasma insulin was higher in low- vs high-birth-weight lambs. Lambs fed ad libitum had greater plasma concentrations of glucose, urea nitrogen, insulin, and IGF-I compared to those fed a restricted diet (ADG = 150 g). The results suggest that during the early postpartum period, newborn lambs exhibit the fetal characteristic of high rates of amino acid oxidation. The results also support the notion that, at birth, low-birth-weight lambs are less mature than high-birth-weight lambs in aspects of metabolic and endocrine development, which may enhance their capacity to utilize amino acids for energy production and to support gluconeogenesis during the immediate postpartum period. Being small at birth also resulted in elevated plasma insulin concentrations when adequate nutriment to support moderate or rapid growth was provided postpartum, although it remains to be elucidated whether this more chronic effect persists in the longer term.
本研究调查了出生体重和产后营养对新生羔羊能量代谢调节的影响。将低出生体重（平均±标准差2.289±0.341千克，n = 28）和高出生体重（4.840±0.446千克，n = 20）的雄性萨福克×（芬兰羊×多塞特羊）羔羊单独用液体饲料饲养，使其从出生到体重（LW）达到约20千克时快速生长（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，体重小的新生羔羊血浆尿素氮浓度（平均±标准误8.31±0.25对6.39±0.32毫摩尔，P = 0.002）和生长激素（ST，49.1±17.0对10.8±4.3纳克/毫升，P = 0.045）较高，而胰岛素样生长因子-I（IGF-I）较低（36.1±6.8对157.7±21.8纳克/毫升，P < 0.001）。血浆葡萄糖（1.42±0.23对2.63±0.95毫摩尔，P = 0.147）和胰岛素（0.09±0.02对0.13±0.06纳克/毫升，P = 0.264）浓度无差异。产后第一周内，所有羔羊血浆尿素氮浓度均先达到峰值然后迅速下降，出生后血浆ST随体重下降。在饲养至20千克体重期间，低出生体重羔羊的血浆胰岛素水平高于高出生体重羔羊。与限饲（平均日增重=150克）的羔羊相比，自由采食的羔羊血浆葡萄糖、尿素氮、胰岛素和IGF-I浓度更高。结果表明，在产后早期，新生羔羊表现出氨基酸氧化率高的胎儿特征。结果还支持这样一种观点，即出生时，低出生体重羔羊在代谢和内分泌发育方面比高出生体重羔羊更不成熟，这可能增强它们在产后即刻利用氨基酸进行能量产生和支持糖异生的能力。出生时体重小在产后提供足够营养以支持适度或快速生长时也会导致血浆胰岛素浓度升高，不过这种更长期的影响是否持续还有待阐明。
