EFFECT OF AMMONIA TREATMENT OF BARLEY STRAW ON THE DYNAMICS OF ITS DEGRADATION IN THE RUMEN

Two experiments were designed to examine the effects of ammonia treatm ent of barley straw on rumen environmental conditions for fibre degrad ation, and to determine the effect of treatment on the soluble and ins oluble fractions of straw. In experiment 1, rumen pH, and ammonia-nitr ogen and volatile fatty acid concentrations in the rumen of sheep rece iving untreated (US1) or ammonia-treated (TS1) straw were recorded. Al so, both straws were incubated in the rumen of both groups of animals. There were no significant differences (P > 0.05) within rumen paramet ers, except for butyrate proportion, which was higher (P < 0.01) with TS1. Dry matter and neutral-detergent fibre disappearances of TS1 were higher (P < 0.001) than those of USI at all the incubation times. Deg radation of both straws in US1-fed sheep was not smaller, and in some periods of incubation was even greater, than in TS1-fed animals. In ex periment 2, samples of untreated (US2) and treated (TS2) straw were in cubated in wethers offered a mixture (50:50) of alfalfa hay and straw. Samples of US2 and TS2 were soaked in autoclaved rumen fluid to measu re their solubility. It was clear that, although treatment increased t he soluble fraction of US2 and TS2 by 52 and 65 g/kg respectively, fro m 0 to 72 h of incubation, increasing the differences between straws f rom 45 to 58 g/kg in that period, actual microbial action on the treat ed roughage was the more important factor, accounting for a difference between US2 and TS2 of 131 g/kg after 72 h incubation.