The rumen fermentativecharacteristics 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 blockdesign with four replications, were evaluated. The dry season supplement had46.9% 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 higherin August in the Ano and Seca treatment, and in the others periods animals inthe treatment Ano had greater proportions. Similarly, the acetate:propianateratio was lower in the supplemented treatments in all periods. The values ofN-NH3 showed an interaction between period and treatment, with theanimals receiving proteic supplement showing higher values in August (Ano andSeca), February and May (Ano. Urea nitrogen showed an interaction between periodand treatment, with supplemented animals showing higher values in August (Anoand Seca), February and May (Ano) than the other treatments, and in Novemberthe Ano treatment was higher than Teste only.
