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

研究表明，生长激素、胰岛素和胰高血糖素是控制能量分布的主要激素，对提高反刍动物产奶量有重要作用。我们之前报道过绵羊体内这些激素的分泌被几种氨基酸修饰（Kuhara et al., 1991）。本研究旨在探讨氨基酸对泌乳山羊体内激素和代谢物浓度的影响。试验1增加日粮以适应维持泌乳所需能量。在试验2中，增加日粮以克服能量需求。在两个实验中，分别以3 mmol/kg体重/30 min的剂量向哺乳期和非哺乳期动物颈静脉输注氨基酸（Asp、Leu、Ala和Gly）中的任意一种。在试验3中，按试验1的能量水平连续给药6 d。在实验1中，GH的分泌量随着氨基酸的增加而增加，而胰岛素的分泌量在哺乳期受到抑制。在哺乳期给药后，氨基酸N浓度的升高受到抑制，而游离脂肪酸浓度的升高得到增强。产奶量与血浆IGF-I浓度之间存在显著的正交互作用。然而，在实验2中，生长激素反应被抑制，胰岛素和胰高血糖素的基础浓度在哺乳期升高。在实验3中，氨基酸的持续输注提高了生长激素、胰岛素和胰高血糖素的浓度，但泌乳期和非泌乳期之间没有显著变化。根据这些结果，我们得出结论，泌乳山羊在维持能量水平下表现出出能反应（分解代谢），而在过量能量水平下则表现出合成反应（合成代谢）。然而，如何提高产奶量还有待进一步的研究。

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.