Greenwood P L, Hunt A S, Bell A W
Department of Animal Science, Cornell University, Ithaca, NY 14853-4801, USA.
J Anim Sci. 2004 Feb;82(2):422-8. doi: 10.2527/2004.822422x.
This study investigated effects of birth weight and postnatal nutrition on organ growth in neonatal lambs. Suffolk x (Finnsheep x Dorset) low- (mean +/- SD 2.29 +/- 0.34 kg, n = 28) and high- (4.84 +/- 0.45 kg, n = 20) birth-weight male lambs were studied. Lambs within each birth weight category were allocated to be individually grown rapidly (ad libitum fed, ADG 337 g, n = 20) or slowly (ADG 150 g, n = 20) on a liquid diet to live weights up to approximately 20 kg. All organs weighed less at birth in small than in large newborns (P < 0.001), except the adrenals (P = 0.10). At birth, as a percentage of empty body weight (EBW), small newborns had larger testes (0.14 vs. 0.10%, P = 0.023) and smaller thymus (0.17 vs. 0.37%, P = 0.009), and tended to have a larger heart (0.85 vs. 0.75%, P = 0.060) and a smaller spleen (0.10 vs. 0.14%, P = 0.054) than large newborns. During the first 2 to 3 wk postpartum, small newborns had greater fractional growth rates of organs than large newborns, most notably spleen, thymus, and liver. Postnatal growth of organs was more closely associated with EBW than age, except for lungs, testes, and stomach. At completion of rearing to 20 kg of live weight, small newborns had a spleen approximately 30% heavier than large newborns (P < 0.001). Testes weights were 37% and 24% greater in small newborns reared slowly and rapidly, respectively, compared with their high-birth-weight counterparts (P = 0.034). It was also evident that postnatal nutrition altered the mass of individual organs at the conclusion of the rearing period without affecting the combined weight of dissected organs. Slowly reared lambs had a larger pancreas (+27%, P = 0.002), stomach complex (+83%, P < 0.001), large intestine (+39%, P < 0.001), entire gastrointestinal tract (+18%, P = 0.002), and testes (+54%, P = 0.016) and tended to have a larger heart (+6%, P = 0.068) than their rapidly reared counterparts at 20 kg of live weight. Rapidly reared lambs had a larger thymus (+61%, P = 0.003), liver (+34%, P < 0.001), kidneys (+33%, P < 0.001), and small intestine (+17%, P < 0.001) and tended to have a larger thyroid (+13%, P = 0.054) at 20 kg of live weight than slowly reared lambs. The functional significance of the smaller thymus at birth and increase in spleen and testes weights at 20 kg of live weight in low- compared with high-birth-weight lambs warrants further investigation. It also remains to be established whether these differences at 20 kg of live weight persist.
本研究调查了出生体重和产后营养对新生羔羊器官生长的影响。研究了萨福克×（芬兰羊×多塞特羊）低出生体重（平均±标准差2.29±0.34千克，n = 28）和高出生体重（4.84±0.45千克，n = 20）的雄性羔羊。每个出生体重组内的羔羊被分配以液体饲料单独快速生长（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）至约20千克体重。除肾上腺外（P = 0.10），出生时小新生羔羊的所有器官重量均低于大新生羔羊（P < 0.001）。出生时，以空体重（EBW）的百分比计算，小新生羔羊的睾丸较大（0.14对0.10%，P = 0.023），胸腺较小（0.17对0.37%，P = 0.009），且心脏往往较大（0.85对0.75%，P = 0.060），脾脏较小（0.10对0.14%，P = 0.054）。在产后的前2至3周，小新生羔羊器官的相对生长率高于大新生羔羊，最显著的是脾脏、胸腺和肝脏。除肺、睾丸和胃外，器官的产后生长与EBW的相关性比与年龄的相关性更密切。饲养至20千克体重结束时，小新生羔羊的脾脏比大新生羔羊重约30%（P < 0.001）。与高出生体重的对应羔羊相比，缓慢饲养的小新生羔羊的睾丸重量分别高37%和24%，快速饲养的小新生羔羊的睾丸重量分别高37%和24%（P = 0.034）。同样明显的是，产后营养在饲养期结束时改变了单个器官的质量，但不影响解剖器官的总重量。在20千克体重时，缓慢饲养的羔羊的胰腺较大（+27%，P = 0.002）、胃复合体较大（+83%，P < 0.001）、大肠较大（+39%，P < 0.001）、整个胃肠道较大（+18%，P = 0.002）、睾丸较大（+54%，P = 0.016），且心脏往往较大（+6%，P = 0.068）。与快速饲养的羔羊相比，在20千克体重时，快速饲养的羔羊的胸腺较大（+61%，P = 0.003）、肝脏较大（+34%，P < 0.001）、肾脏较大（+33%，P < 0.001）、小肠较大（+17%，P < 0.001），且甲状腺往往较大（+13%，P = 0.054）。与高出生体重羔羊相比，低出生体重羔羊出生时胸腺较小以及在20千克体重时脾脏和睾丸重量增加的功能意义值得进一步研究。20千克体重时的这些差异是否持续也有待确定。
