Feeding a High-Concentrate Diet Reduces Milk Production is Associated with Endogenous Growth Hormone in Lactating Goats.

The aim of this work was to evaluate the effects of endogenous GH-IGF-1 axis on lactating goats fed with high-concentrate diets. Ten lactating goats were used and randomly divided into two groups, in a 2×2 Latin square experiment design with different forage to concentrate rations of 40:60 (the control group) and 60:40 (the high-concentrate group), respectively. During the experiment, milk samples were collected to assay the content of milk compositions; plasma samples were collected to measure the content of IGF-1 and GH. The liver and mammary gland samples were collected to observe the expression of IGF-1R and GH. The results showed that compared with the control group, the content of plasma GH and IGF-1 were decreased in the high-concentrate group, and the percentage of lactose and milk yield were also decreased. Meantime, the mRNA expression of IGF-1R in mammary gland was down-regulated in the high-concentrate group. Our results indicated that feeding with high-concentrate diets for 9 weeks would decrease the contents of endogenous GH and IGF-1, and eventually lead to the decreased milk yield. [ABSTRACT FROM AUTHOR]