Studies on Ruminal Urease Activity

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Abstract
Four rumen fistulated steers were used in each of three switch back trials and six rumen fistulated steers in a fourth trial to test the effects of (1) fasting vs. feeding a mixed diet, (2) a mixed vs. a cottonseed hulls diet, (3) a good quality alfalfa vs. a poor quality prairie hay diet on total ruminal urease activity, volatile fatty acid concentrations and (4) the effect of fasting and feeding a mixed and high roughage diet on ruminal fluid pH. Fasting caused lower (P<.01) ruminal ureolytic activity and volatile fatty acid levels than feeding. Ureolytic activity decreased with time on experiment in animals fasted or fed the mixed diet. Fatty acid levels were not affected by time on feed. Differences in ureolytic activity were not significant (P>.05) between steers fed the mixed diet vs. those fed the roughage rations. Feeding the mixed diet promoted greater (P<.01) levels of total volatile fatty acids, propionic, butyric, and valeric acids but lower (P<.01) levels of acetic acid. No significant differences in ureolytic activity were observed between steers fed good quality alfalfa vs. poor quality prairie hay. Alfalfa hay promoted greater (P<.01) total ruminal concentrations of volatile fatty acids than did prairie hay but did not affect the molar percentages of individual acids. Fasting promoted higher (P<.01) ruminal pH values than feeding the mixed or cottonseed hulls diets. Ruminal pH was lower when the mixed rather than the cottonseed hulls diet was fed. Copyright © 1968. American Society of Animal Science . Copyright 1968 by American Society of Animal Science

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