Graduate School of Biosphere Science, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8528, Japan.
Anim Sci J. 2013 Apr;84(4):310-5. doi: 10.1111/asj.12001. Epub 2012 Nov 19.
Ghrelin action, which stimulates growth hormone (GH) secretion, may alter during the weaning period in calves. Our objective was to compare the effects of intravenous ghrelin injection on plasma GH, insulin and glucose concentrations in calves around the weaning period. Four Holstein bull calves were fed whole milk and allowed free access to solid feeds, and weaned at 7 weeks of age. Measurements were performed at weeks 1, 2, 4, 6, 7, 9, 11 and 13, when calves were intravenously injected with ghrelin (1.0 μg/kg body weight (BW)) through a catheter, and jugular blood samples were obtained temporally relative to the injection time. Estimated digestible energy intake per metabolic BW transiently decreased at week 7 because of low solid intake immediately after weaning, and thereafter gradually increased. Plasma insulin and glucose concentrations were not affected by ghrelin injection at all ages. In contrast, plasma GH concentrations increased with ghrelin injection at all ages. The incremental area of GH at week 7 was greatest and significantly higher compared with weeks 2, 4, 6 and 9. This result suggests that nutrient insufficiency immediately after weaning enhances GH responsiveness to ghrelin.
胃饥饿素的作用是刺激生长激素（GH）的分泌，这种作用可能会在犊牛断奶期间发生改变。我们的目的是比较在断奶期前后静脉注射胃饥饿素对犊牛血浆 GH、胰岛素和葡萄糖浓度的影响。4 头荷斯坦公牛犊用全乳喂养，并允许自由采食固体饲料，在 7 周龄时断奶。在 1、2、4、6、7、9、11 和 13 周时，通过导管给犊牛静脉注射胃饥饿素（1.0μg/kg 体重（BW）），并在注射时间的时间点采集颈静脉血样。由于断奶后立即固体采食量低，估计代谢 BW 的可消化能量摄入量在第 7 周暂时下降，此后逐渐增加。GH 浓度不受 GH 注射的影响。相比之下，在所有年龄段，血浆 GH 浓度均随 GH 注射而增加。第 7 周的 GH 增量面积最大，与第 2、4、6 和 9 周相比显著更高。这一结果表明，断奶后营养不足会增强 GH 对胃饥饿素的反应性。
