Title: Relation of Nitrogen Intake to Rumen Microbial Activity and Consumption of Low-Quality Roughage by Sheep
Abstract: The activity of rumen microorganisms in relation to consumption of low-quality range grasses by sheep with and without supplementation was evaluated in terms of gas and VFA production. Low-quality range forage was supplemented with urea alone, urea plus VFA, urea plus caproic acid, and casein alone. All supplements increased voluntary feed consumption, microbial activity, dry matter digestibility, concentration of rumen VFA and microbial protein and blood urea levels, but not blood glucose. However, none of the supplements enhanced these parameters significantly above the levels produced by urea alone. This indicated that rumen microorganisms appear to be capable of synthesizing their essential cellular components utilizing urea alone as a source of nitrogen. Reduction of intake on the control diet of unsupplemerited range grass was considered to result from the nitrogen deficiency in this ration with consequent lowering of bacterial activity. However, progressive increases in consumption during treatment periods reflect increased microbial activity. After the first series of trials, microbial activity and consumption continued to increase progressively in apparent response to the carry over effects of enhanced nitrogen supplementation.