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

(1)研究了日粮精料含量(0%、40%和80%)对6只成年杂交绵羊生长激素(GH)、胰岛素样生长因子-I(IGF-I)和胰岛素分泌的影响。各处理组饲喂后血浆GH浓度均显著降低，并分别持续8小时(0%)和12小时(40%、80%)。0%、40%和80%浓缩饲料处理组的24小时生长激素平均浓度分别为10.4、7.9和5.6 ng/ml。它们彼此之间有很大的不同。饲喂40%和80%精料饲料后，动物血浆胰岛素浓度显著升高，而饲喂0%精料饲料时，动物血浆胰岛素浓度仅略有升高。(2)瘤胃内和十二指肠内注入酪蛋白和淀粉对绵羊GH、IGF-I和胰岛素分泌的影响。每天饲喂果园干草一次，连续饲喂4小时(1400-1800)。在4小时内注入酪蛋白和淀粉。瘤胃内和十二指肠内注入酪蛋白后，与对照组相比，饲喂后血浆GH浓度持续下降。瘤胃内注入淀粉也可引起生长激素的持续下降，但十二指肠内注入淀粉不影响饲喂后生长激素的下降。(3)饲喂后VFA浓度升高可能在绵羊饲喂后生长激素分泌下降中起重要作用。

(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.