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Urease Activity in Bovine Feces

USDA — ARS, Ithaca, NY 14853

ABSTRACT

The objectives were to measure the urease activity of bovine feces as affected by urea concentration, temperature, and pH and to determine if such activity predicts urea decomposition in urine-feces mixtures. Urease activity was measured with urea solutions and fresh bovine feces. Michaelis-Menten kinetics described the variation in the activity of feces as a function of urea concentration. Maximum activity and the Michaelis constant increased with temperature between 10 and 40° C in an Arrhenius manner with activation energies of 12,840 and 11,800 cal/ g-mole, respectively. Maximum urease activity occurred between pH 6.8 and 7.6. On both sides of this range, activity decreased linearly with pH. Urea decomposition in urine-feces mixtures with time was predicted reasonably by urease activity of feces.

Greater than 95% urea decomposition in urine on a typical freestall barn floor should occur within 6 h at 30°C and within 24 h at 10°C. Thus, nitrogen losses from dairy manure (urine plus feces) of up to 50% of total nitrogen are possible in a barn scraped once daily.

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