The rumen fermentative characteristics of Nelore steers grazing Brachiaria Brizantha pastures (Teste), or supplemented during the dry season (Seca), dry and wet seasons (Ano) or with free access to a Leucaena bank (Banco), in a randomized block design with four replications, were evaluated. The dry season supplement had 46.9% CP, 70% rumen degradable, and the wet season supplement, 43.9%CP, 60% degradable. Rumen liquor was collected on August, November, February and May. The molar proportions of propionic acid in the supplemented animals were higher in August in the Ano and Seca treatment, and in the others periods animals in the treatment Ano had greater proportions. Similarly, the acetate:propianate ratio was lower in the supplemented treatments in all periods. The values of N-NH3 showed an interaction between period and treatment, with the animals receiving proteic supplement showing higher values in August (Ano and Seca), February and May (Ano. Urea nitrogen showed an interaction between period and treatment, with supplemented animals showing higher values in August (Ano and Seca), February and May (Ano) than the other treatments, and in November the Ano treatment was higher than Teste only.
beef cattle; feed supplement; grazing; rumen fermentation; rumen amonia nitrogen; urea nitrogen; volatile fatty acids
