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ARS Home » Northeast Area » Ithaca, New York » Robert W. Holley Center for Agriculture & Health » Research » Publications at this Location » Publication #60581
Title: THE EFFECT OF AMINO NITROGEN ON THE ENERGETICS OF RUMINAL BACTERIA AND ITS IMPACT ON ENERGY SPILLING

Author
item VAN KESSELL, JO ANN - CORNELL UNIVERSITY
item Russell, James

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/29/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Providing adequate protein is a major cost of production by ruminant farm animals (cattle, sheep, goats). Microbial protein, which is synthesized in the rumen, is the major source of amino acids for ruminant animals. Current National Research Council Recommendations are based on the assumption that the growth efficiency of ruminal bacteria is constant, but previous experiments have indicated that the growth efficiency of ruminal bacteria could be increased by supplying amino acid nitrogen. Our work indicated that addition of amino acid nitrogen increases the growth rate of ruminal bacteria, allows them to better match the rates of anabolic (synthesis) and catabolic (degradation) rates, and prevents them from wasting energy. The benefit is apt to be greatest when the rate of carbohydrate fermentation in the rumen is rapid. These findings contribute to efforts aimed at increasing the production efficiency of ruminant animals.

Technical Abstract: When mixed ruminal bacteria were provided with an excess of soluble carbohydrates, Streptococcus bovis dominated the population and lactate was the predominant fermentation end-product. The overgrowth of S. bovis could be counteracted by diluting the ruminal fluid 10 8-fold. The bacteria that were present at greater than 10 8/ml did not decarboxylate succinate, but succinate accumulation was overcome by the addition of Selenomonas ruminantium H18. Methanogenic bacteria did not persist, but the culture always had a variety of morphological types. The mixed ruminal bacteria grew rapidly (.32 h-1) in batch culture on soluble carbohydrates and ammonia, but the growth rate could be increased by as much as 1-fold if protein hydrolyzaes were added. The bacteria had a high affinity for gelatin hydrolyzate, but casein and soy hydrolyzates provided higher maximum growth rates. The protein hydrolyzates increased the yield of the bacteria, but the increase in yield was 10-fold greater than the amount predicted by maintenance energy. Based on these results, it appeared that protein hydrolyzates allowed the bacteria to decrease their rate of energy spilling. Because the impact of energy spilling is greatest when there is a large imbalance between anabolic and catabolic rates, one would expect the greatest benefit from ruminally degraded protein when the rate of carbohydrate fermentation in the rumen is rapid.