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Abstract

Two experiments were carried out to measure ruminal ammonia production from five different protein sources, as an index of protein degradation by rumen microbes. In the first experiment, two rumen fistulated ewes were used in a 2 x 5 x 2 x 9 (animals x protein sources x trials x sampling times) factorial design. Five proteins of variable solubilities were used: fishmeal, soybean meal, linseed meal, meat scraps and casein. Changes in ruminal ammonia concentration were measured during a six-hour period to determine ammonia concentration curves which were used as indicators of the relative degradation of the protein sources in the rumen. Casein produced greater changes in ammonia concentration that the other protein sources (P<.01). Linseed meal, soybean meal and meat scraps were degraded to a lesser extent. Fishmeal, apparently was the least degraded source, because it produced negative changes in ruminal ammonia concentrations in relation to the time of ifusion. In the second experiment, a series of incubation trials with rumen liquor from a fistulated cow, were conducted with the same protein sources utilized in the in vivo experiment. A 5 x 3 x 2 x 3 (protein sources x trials x repetitions x incubation times) factorial design was utilized. There were significant differences in ammonia production from the different sources starting after 12 hours of incubation. A the 24 hours incubation period there were significant diferences in ammonia production, this indicating that probably casein was the most degraded protein, followed by soybean meal, linseed meal and meat scraps. Apparently, fish meal was the least degraded protein. From both experiments, the responses were similar, it was concluded that being casein the most degraded protein source and fish meal the least degraded. Soybean meal, linseed meal and meat scraps showed intermediate values in relation to the other two protein sources.