The Influence of Different Protein Supply and Feeding Level on pH, Ammonia Concentration and Microbial Protein Synthesis in the Rumen of Cows

Abstract

Rumen ammonia concentration and pH was measured every second hour throughout 24 hours in an experiment including 33 periods with 2–5 rumen and duodenal cannulated cows. The calculated microbial non ammonia nitrogen synthesis was related to the mean NH₃ concentration the hours with an NH₃ concentration below 2, 5, 10, 15 and 20 mg NH₃-N per 100 ml rumen fluid and the calculated protein balance in the rumen (PBV). The results showed no influence on rumen NH₃ concentration of feeding the same ration composition on two levels, although the pH was significantly depressed by the higher feeding level. There was good agreement between the calculated PBV and the measured mean NH₃-concentration in the rumen. The microbial protein synthesis per kg totally digested carbohydrates was not influenced by the PBV or NH₃ concentration within the observed range in the experiments. The results further showed, that there is a significant variation in the microbial protein synthesis which can neither be described to the amount of digested carbohydrates nor to the PBV or ammonia supply of the rumen microorganisms.

Key Words:

• nitrogen
• diurnal variation