INFLUENCE ON SOME RUMEN AND BLOOD PARAMETERS OF FEEDING ACETOHYDROXAMIC ACID IN A UREA-CONTAINING RATION FOR LAMBS

Abstract

A 4 × 4 latin square design experiment, involving four fistulated Dorset–Columbia crossbred lambs, was used to determine the effects of feeding the urease inhibitor acetohydroxamic acid (AHA) with a urea-containing ration on some parameters of the rumen fermentation and blood. AHA, administered in the feed at concentrations up to and including 1.5%, markedly depressed rumen urease activity and the peak concentration of rumen ammonia. The maximum AHA concentration achieved in the rumen solution was 32.29 ± 14.26 mg per 100 ml, and thereafter the concentration dropped by 66% during the next 2 h. No evidence was found for an effect of AHA upon rumen pH, viable bacterial count, total protozoal count, total volatile fatty acid concentration, molar ratios of acetate, propionate and n-butyrate, or upon blood urea-nitrogen concentration. Traces of AHA were found in peripheral blood both 1 and 3 h after feeding, showing that AHA is absorbed from the ruminant digestive tract. It was concluded that AHA did not influence major parameters of the rumen fermentation at concentrations that effectively inhibited rumen urease.