Dwyer C M, Morgan C A
Sustainable Livestock Systems Group, SAC, Edinburgh, EH9 3JG, UK.
J Anim Sci. 2006 May;84(5):1093-101. doi: 10.2527/2006.8451093x.
To survive, the newborn lamb must be able to maintain body temperature and to stand and move to the udder to suck colostrum to fuel heat production. The objective of this study was to investigate whether neonatal lambs showing slow behavioral progress to standing and sucking also have an impaired ability to maintain body temperature. The time taken to stand and suck after birth, rectal temperatures, and blood samples were collected from 115 newborn single, twin, and triplet lambs of 2 breeds, Scottish Blackface and Suffolk, which are known to show variations in their neonatal behavioral progress. Blood samples were assayed for thyroid hormones, known to be involved in heat production, and cortisol, which plays a role in tissue maturation before birth. In addition, colostrum samples were collected from the 56 ewes that gave birth to the lambs, and assayed for protein, fat, and vitamin contents. Heavy lambs (more than 1 SD above the breed mean), Blackface lambs, and singleton or twin lambs were quicker to stand and suck from their mothers than lightweight (more than 1 SD below the breed mean), Suffolk, or triplet lambs. Low birth weight lambs also had lower rectal temperatures than heavier lambs (P < 0.01), as did Suffolk compared with Blackface lambs (P < 0.001). Lambs that were slow to suck after birth had lower rectal temperatures than quick lambs, and this difference persisted for at least 3 d after birth. Within breed, heavy lambs had greater plasma triiodothyronine and thyroxine immediately after birth than light lambs. Blackface lambs had greater plasma triiodothyronine and thyroxine than Suffolk lambs but tended to have less cortisol. Colostrum produced by Blackface ewes had a greater fat content than that of Suffolk ewes (P < 0.001). Thus, lambs that are behaviorally slow at birth are also less able to maintain their body temperature after birth. Although part of their lower body temperature might be attributable to behavioral influences on thermoregulation, the data also suggest that physiological differences exist between these animals. These differences may be related to different degrees of maturity at birth.
为了存活，新生羔羊必须能够维持体温，站立并移动到乳房处吮吸初乳以获取产热所需的能量。本研究的目的是调查行为上站立和吮吸进展缓慢的新生羔羊维持体温的能力是否也受损。从115只出生的单胎、双胎和三胞胎新生羔羊中收集出生后站立和吮吸所需的时间、直肠温度及血样，这些羔羊分属两个品种，即苏格兰黑脸羊和萨福克羊，已知它们在新生期行为进展存在差异。检测血样中的甲状腺激素（已知其参与产热）和皮质醇（其在出生前的组织成熟过程中起作用）。此外，从产下羔羊的56只母羊中收集初乳样本，检测其蛋白质、脂肪和维生素含量。体重较重的羔羊（超过品种均值1个标准差以上）、黑脸羊以及单胎或双胎羔羊比体重较轻的羔羊（低于品种均值1个标准差以上）、萨福克羊或三胞胎羔羊更快站立并从母亲处吮吸。出生体重低的羔羊直肠温度也低于体重较重的羔羊（P < 0.01），萨福克羊与黑脸羊相比也是如此（P < 0.001）。出生后吮吸缓慢的羔羊直肠温度低于吮吸迅速的羔羊，且这种差异在出生后至少持续3天。在同一品种内，体重较重的羔羊出生后即刻血浆三碘甲状腺原氨酸和甲状腺素水平高于体重较轻的羔羊。黑脸羊的血浆三碘甲状腺原氨酸和甲状腺素水平高于萨福克羊，但皮质醇水平往往较低。黑脸母羊产出的初乳脂肪含量高于萨福克母羊（P < 0.001）。因此，出生时行为迟缓的羔羊出生后维持体温的能力也较弱。虽然它们较低的体温部分可能归因于行为对体温调节的影响，但数据也表明这些动物之间存在生理差异。这些差异可能与出生时不同程度的成熟度有关。
