In Vitro Inhibition of Rumen Urease with Acetohydroxamic Acid

THE efficiency of urea utilization by ruminants is limited by its rapid hydrolysis by urease and loss of large amounts of nitrogen due to absorption of ammonia through the rumen wall and into the bloodstream. Acetohydroxamic acid (HONHC:OCH3) has inhibited intestinal urease in uremic humans (Fishbein, Carbone and Hochstein, 1965) and rumen fluid urease (Baintner, 1964, 1967; Brent and Adepoju, 1967). Streeter (1969) found the effectiveness of AHA against sheep rumen fluid urease decreased over a 5-day period, when fed at 90, 180 or 360 mg per kilogram body weight. However, Portela (1968) found no adaptive or residual effect in steers when AHA was given at about 8 or 16 mg per kilogram body weight. In vitro studies reported here were designed to further evaluate acetohydroxamic acid (AHA) as a ruminal urease inhibitor. Partially purified urease from rumen contents was used to examine the kinetics and reversability of AHA inhibition.