Abstract

MOTA, M.F. et al. Parameters of rumen fermentation of dairy cows grazing tropical forage. Arch. zootec. [online]. 2010, vol.59, n.226, pp.217-224. ISSN 1885-4494.

Four lactating dairy cows fitted with ruminal cannula were used to study two levels of concentrate supplementation (treatments), low (BC), 2.67 or high (AC), 5.37 kg of DM/day. Animals were assigned in intermittent grazing Coastcross forage during the summer with a stocking rate of five animal units/hectare. The chemical composition of the concentrate was the same in both treatments and it was divided in equal part to feed the cows at the morning and at the afternoon milking. The aim of this study was to evaluate the ruminal parameters: pH, ammonia nitrogen (N-NH₃) concentration and volatile fatty acids (AGV) concentration. The Coastcross had on average 11.7% of PB, 70.2% of FDN, 35.2% of FDA and 63.8% of in vitro digestibility of dry-matter (DIVMS). The average of dry matter intake was 13.6 kg and 14.6 kg. The chemical composition of the diets was 13.6% and 15.2% of PB, 2.6% and 3.2 of EE, 64.0% and 59.0% of FDN for BC and AC treatments, respectively. The increase of the concentrate in diet, influenced rumen pH, however the values not affect cellulose-digesting activity of the rumen microorganisms. The values of N-NH₃ and total AGV of the rumen fluid did not change with the different levels of concentrate.

Keywords : VFA; Coastcross; Bermuda grass; Cynodon dactylon; Grass dairy production; Ruminant production.

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