PSXI-15 Effect of peptides and corn processing on in vitro rumen fermentation and microbial protein synthesis.

摘要

Increasing the microbial crude protein (MCP) synthesis in rumen has been shown to increase both milk and milk protein yields. Sources of dietary energy and nitrogen affect MCP synthesis. It has been demonstrated that peptides are one of the important substrates required for rumen MCP synthesis. This study aims to investigate the effect of supplementation of peptides to ground corn or steam corn based diets on rumen fermentation and MCP synthesis using in vitro batch culture. Peptide was extracted from cottonseed (45 % purity, Mytech Biotech Co., Ltd. China). Peptide was added at the levels of 0, 0.25, 0.5, 0.75% DM to ground corn-based (GC) or steam-flaked corn-based diets (SFC). Treatments were arranged with a 2x4 factorial design. Each treatment contains 4 flasks and experiment was repeated three times. Four flasks from each treatment were taken out at 3, 6, 9, 12, 24, and 48 h and ruminal fluid was analyzed to determine pH, ammonia-N (NH3-N), volatile fatty acids (VFAs) composition, and MCP. The results suggest that pH of ruminal fluid was not (P > 0.05) affected by peptides and was slightly decreased as rumen fermentation proceed, but all values were found to be in the normal range. NH3-N concentration decreased significantly in SFC (25.32 ± 0.27 mg/dL) as compared to GC (26.34 ± 0.28 mg/dL, P=0.0113). While no significant (P > 0.05) change occurred for the concentration of MCP and NH3-N among the treatments. Concentrations of individual and total VFAs were not significantly (P>0.05) affected by peptides. However, compared with GC, the SFC increased the propionate production (20.80 ± 0.11 % vs 21.74 ± 0.11 %, PP=0.0069). Results indicate that peptides changed rumen fermentation with different release rate of energy diets in vitro, while did not affect MCP synthesis.