Taylor V J, Beever D E, Bryant M J, Wathes D C
Department of Veterinary Basic Sciences, Royal Veterinary College, University of London, Hatfield AL9 7TA, UK.
J Endocrinol. 2004 Jan;180(1):63-75. doi: 10.1677/joe.0.1800063.
The aim of this study was to determine whether any differences in the GH-IGF-I axis in juvenile calves were predictive of fertility problems as adult cows. Endogenous metabolic hormone profiles before and after feeding and the response to a GH-releasing factor (GRF) challenge were measured in prepubertal (6 month) dairy calves. These metabolic parameters were subsequently related to physical characteristics at puberty and to ovarian function during the first lactation. Milk progesterone analysis was used to categorize the animals into those with normal progesterone profiles following calving (n=17) and those that developed delayed ovulation (DOV1, n=9) or persistent corpus luteum (PCL1, n=6) profiles. There were associations between prepubertal GH parameters, glucose and non-esterified fatty acid (NEFA) concentrations and the body condition score at which the animals attained puberty. The calves which subsequently developed DOV1 profiles as cows tended to have a higher GH pulse amplitude during fasting than normal profile animals, they did not show the anticipated decrease in circulating glucose concentrations following a post-prandial rise in insulin and they also had the lowest IGF-I concentrations. The calves that later developed PCL1 had a significantly larger GH pulse amplitude and pulse area than normal profile animals in the fed period and had the highest IGF-I concentrations. There were no differences in prepubertal insulin or NEFA concentrations or in the GH response to a GRF challenge between the different progesterone profile categories. Plasma IGF-I concentrations in prepubertal animals were positively correlated with their post-calving concentrations, whereas glucose concentrations had a negative correlation between these time-periods. These results suggested that the different juvenile endocrine profiles of the DOV1 cows may predispose them to a higher rate of tIssue mobilization during lactation and a consequent reduction in fertility, while altered GH and IGF-I levels in PCL1 cows may later contribute to the maintenance of the persistent corpus luteum. Therefore metabolic differences in prepubertal calves were later reflected by altered reproductive function during the first lactation.
本研究的目的是确定幼年犊牛生长激素-胰岛素样生长因子-I（GH-IGF-I）轴的任何差异是否可预测其成年后作为母牛时的繁殖问题。在青春期前（6月龄）的奶牛犊中测量了采食前后的内源性代谢激素谱以及对生长激素释放因子（GRF）刺激的反应。随后将这些代谢参数与青春期的身体特征以及首次产犊期间的卵巢功能相关联。通过牛奶孕酮分析将动物分为产后孕酮谱正常的动物（n = 17）以及出现排卵延迟（DOV1，n = 9）或黄体持久化（PCL1，n = 6）谱的动物。青春期前的GH参数、葡萄糖和非酯化脂肪酸（NEFA）浓度与动物达到青春期时的体况评分之间存在关联。后来作为母牛出现DOV1谱的犊牛在禁食期间往往比孕酮谱正常的动物具有更高的GH脉冲幅度，它们在餐后胰岛素升高后循环葡萄糖浓度未出现预期的下降，并且它们的IGF-I浓度也是最低的。后来出现PCL1的犊牛在采食期的GH脉冲幅度和脉冲面积明显大于孕酮谱正常的动物，并且具有最高的IGF-I浓度。不同孕酮谱类别之间在青春期前的胰岛素或NEFA浓度以及对GRF刺激的GH反应方面没有差异。青春期前动物的血浆IGF-I浓度与其产后浓度呈正相关，而葡萄糖浓度在这些时间段之间呈负相关。这些结果表明，DOV1母牛不同的幼年内分泌谱可能使它们在泌乳期间组织动员率更高，从而导致繁殖力下降，而PCL1母牛中GH和IGF-I水平的改变可能随后有助于黄体的持续存在。因此，青春期前犊牛的代谢差异在首次产犊期间通过生殖功能的改变得以体现。
