Lactogenic actions of amino acids by activating endocrine systems in the ruminant.

生长激素（GH）、胰岛素和胰高血糖素是控制反刍动物能量分配的主要激素，有助于提高产奶量。我们先前报道了这些激素的分泌被绵羊中的几种氨基酸修饰（Kuhara等人，1991年）。本研究旨在探讨日粮中添加氨基酸对泌乳山羊体内激素及代谢产物含量的影响。在实验2中，增加日粮以克服能量需求。在两个实验中，将任一种氨基酸（Asp、Leu、Ala和Gly）以3 mmol/kg B.W./在实验3中，在实验1的能量水平下连续给药6天。在实验1中，在泌乳期，响应于氨基酸给药的GH分泌增量增强，而胰岛素分泌增量被抑制。氨基氮浓度的上升受到抑制，但FFA浓度的增加，在泌乳期的管理响应。产奶量与血浆IGF-I浓度呈显著正相关。然而，在实验2中，GH反应被抑制，胰岛素和胰高血糖素的基础浓度在泌乳期增加。试验三连续输注氨基酸可提高泌乳期和非泌乳期奶牛的GH、胰岛素和胰高血糖素浓度，但差异不显著。从这些结果中，我们得出结论，泌乳山羊表现出放能反应（categonic）在维持能量水平，而他们的合成反应（anastrophic）在过剩的能量水平。但是，提高产奶量的方法还有待进一步研究。

It is established that growth hormone (GH), insulin and glucagon are major hormones to control energy distribution, contributing to increase milk yield in the ruminants. We previously reported that the secretion of these hormones was modified by several amino acids in sheep (Kuhara et al., 1991). The aim of the present study was to investigate the effects of administration of amino acids on hormone and metabolite concentrations in lactating goats.In Experiment 1, the ration was increased to fit the energy requirement for maintenance of lactation. In Experiment 2, the ration was increased to overcome the energy requirement. In both Experiments, either of amino acids (Asp, Leu, Ala and Gly) was infused into the jugular vein of lactating and non-lactating animals at 3 mmol/kg B.W./30 min. In Experiment 3, the administration was continued for 6 days at the energy level of Experiment 1.In Experiment 1, secretory increment of GH in response to the amino acid administration was enhanced, while that of insulin was suppressed during the lactating period. A rise in amino N concentration was suppressed, but that in FFA concentration was enhanced, in response to the administration during the lactating period. A significantly positive interaction was observed between milk yield and plasma IGF-I concentration. In Experiment 2, however, GH response was suppressed, and the basal concentration of insulin and glucagon was increased during the lactating period. In Experiment 3, the concentration of GH, insulin and glucagon was raised by the continuous infusion of amino acid, but the significant change was not found between lactaing and non-lactating periods. From these results, we conclude that lactating goats showed exergonic reactions (catabolism) at the maintenance energy level, whereas they did synthetic reactions (anabolism) at the excess energy level. However, further study on the method to increase milk yield remains to be investigated.