Studies on the inhibitory effect of increased VFA concentrations in the rumen after feeding on GH secretion in sheep

(1)研究了饲粮精料含量（0%、40%和80%）对6只杂交成羊生长激素、IGF-I和胰岛素分泌的影响。饲喂后各饲粮处理的血浆生长激素浓度均显著下降，下降时间分别为8小时（0%）和12小时（40%、80%）。0%、40%和80%浓缩日粮处理的GH平均24小时浓度分别为10.4、7.9和5.6 ng/ml。这些都有很大的不同。饲喂40%和80%精料饲粮时，饲后血浆胰岛素浓度显著升高，饲喂0%精料饲粮时，血浆胰岛素浓度略有升高。与生长激素和胰岛素相比，饲喂后血浆IGF-I浓度没有变化。(2)研究了绵羊瘤胃内和十二指肠内输注酪蛋白和淀粉对生长激素、IGF-I和胰岛素分泌的影响。动物每天饲喂一次果园草干草，持续4小时（1400-1800）。4小时内注入酪蛋白和淀粉。与对照组相比，饲喂后瘤胃内和十二指肠内输注酪蛋白均引起血浆生长激素浓度持续下降。瘤胃内输注淀粉也导致生长激素的持续下降，但十二指肠内输注淀粉对饲喂后生长激素的下降没有影响。(3)由此可见，饲后VFA浓度的升高可能对羊饲后生长激素分泌的减少起重要作用。

(1) Effects of dietary concentrate content (0%, 40% and 80%) on GH, IGF-I and insulin secretion were investigated in six adult, crossbred sheep. Significant decreases of plasma GH concentrations were observed after feeding in all dietary treatments and these decreases were continued for 8 hours (0%) and 12 hours (40%, 80%), respectively. Mean 24-hour concentrations of GH were 10.4, 7.9 and 5.6 ng/ml for 0%, 40% and 80% concentrated diet treatments, respectively. These were significantly different from each other. Marked increases in plasma insulin concentrations after feeding were observed when animals were fed the 40% and 80% concentrate diets, whereas only slight increase was detected when animals were fed 0% concentrate diet. Plasma IGF-I concentrations were not changed after feeding in contrast to GH and insulin.(2) Effects of intra-ruminal and intra-duodenal infusion of casein and starch on GH, IGF-I and insulin secretion were tested in sheep. Animals were fed orchard grass hay once daily with food available for 4 hours (1400-1800). Casein and starch were infused during the 4 hours. Both of intra-ruminal and intra-duodenal infusion of casein caused prolonged decreases in plasma GH concentrations after feeding compared with control. Intra-ruminal infusion of starch also caused prolonged decrease in GH, but intra-duodenal infusion of starch did not affect the GH decrease after feeding.(3) It is concluded that increased VFA concentrations after feeding may play an important role in the decrease of GH secretion after feeding in sheep.