Degradation of L-arginine and N-carbamoyl glutamate and their effect on rumen fermentation in vitro

Abstract

The objective of this experiment was to determine the degradation of L-arginine (ARG) and N-carbamoyl glutamate (NCG) and to examine their effect on rumen fermentation. Rumen fluids were collected from 3 rumen-fistulated cows and then incubated with ARG or NCG at 1 mmol/L in a glass syringe system at 39°C for 24 h. The control treatment was given neither ARG nor NCG. Gas production (GP) was recorded, and pH at 2, 4, 6, 12, and 24 h was also determined. At 12 and 24 h, the measurements were also made for ammonia-nitrogen (N), volatile fatty acids (VFA) and microbial crude protein (MCP) yield on purine quantification basis. At 24 h, the proportion of ARG and NCG degradation in rumen fluid was 100.0 and 17.8%, respectively. Gas production and the acetate to propionate ratio increased in groups treated with ARG and NCG, compared with the control (P<0.01). Ammonia nitrogen concentration was higher (P<0.01) in the ARG group than in the NCG and control groups. Microbial crude protein concentration diminished in ARG and NCG groups, in comparison with the control (P<0.01). In conclusion, the effects of ARG and NCG on rumen fermentation were numerically relatively similar. Rapid degradation of ARG in rumen is a nutritionally wasteful process. Thus, ARG should be spared from rumen degradation, while NCG could be fed to ruminant without need for coating.

Key Words:

• Arginine
• Fermentation variables
• In vitro
• N-carbamoyl glutamate
• Rumen degradation.

Acknowledgments:

this study was partly supported by the China Agriculture Research System (CARS-37) and by a grant from the Key Project of Science and Technology Department of Zhejiang Province (No. 2008C12050).

The authors are thankful to Dr. Qiao Shiyan (MOA Feed Industry Centre, China) for his technical support to determine NCG in rumen fluid.