Effects of High-Grain Diet with Buffering Agent on the Milk Protein Synthesis in Lactating Goats

Abstract

Feeding of straw as main roughage with numerous high-grain diets improves the performance of ruminants but it can easily lead to subacute ruminal acidosis. In recent years, buffering agent is applied to prevent the acid poisoning of ruminants and improve the production performance of ruminants in animal husbandry. it is necessary to understand feeding high-grain diet with buffering agent which transport carriers amino acids mainly take amino acids into the mammary gland and the signal mechanism of amino acids in the mammary gland synthesize milk proteins. To gain insight on the effects of a high-grain diet with buffering agent on the amino acids in the jugular blood, and the effects of amino acids on the synthesis of milk protein, commercial kit and high performance liquid chromatography (HPLC) were applied to determine the concentration of amino acids of jugular blood samples, quantitative real-time PCR, comparative proteomic approach and western blot were employed to investigate proteins differentially expressed in mammary tissues and the mechanism of amino acids on the synthesis of milk protein in mammary gland of lactating dairy goats fed high-grain diet with buffering agent or only high-grain diet. Results showed that feeding high-grain diet with buffering agent to lactating dairy goats could outstanding increase amino acid content of jugular blood (p<0.05), and mRNA transcriptional level of amino acid transporters in the mammary gland were also increased; the CSN2 and LF protein expression level were significant higher by 2-DE technique, MALDI-TOF/TOF proteomics analyzer and western blot analysis further validated in mammary of lactating dairy goats compared with high-grain group; the research on the mechanism of milk protein synthesis increasing suggested that it was related to the activation of mTOR pathway signaling. Feeding of high-grain diet with buffering agent promoted the jugular vein blood of amino acids concentration, and more amino acids flowed into the mammary. In addition, milk protein synthesis was increased and the increase of milk protein synthesis was related to the activation of mTOR pathway signalling.