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Chemical composition and in situ dry matter degradability of tropical forages grasses in Northeastern Brazil
Brazil has an area of more than 220 million hectares of pasture, and at least 100 million hectares are cultivated pastures. Thus, tropical grasslands represent an important resource for the Brazilian cattle industry. The chemical composition and ruminal in situ dry matter (DM) degradability of nine tropical forages grasses in Baixo Parnaíba, Maranhão were evaluated. The forages were harvested at 35 days of growth and the cutting height was 15 cm of soil. One Santa Inês male sheep (BW 63 kg) cannulated in the rumen was used for feed incubation. Samples of 5 grams of each forage were incubated in the rumen in nylon bags. For each time of incubation four bags were used. The experiment followed a completely randomized design in a 3x9 factorial arrangement (three times of incubation – 6, 24 and 96 h and nine species - Brachiaria humidicola, Brachiaria hybrid cv. Mulato, Brachiaria brizantha cvv. Piatã, Xaraés and Marandu, Brachiaria ruziziensis, Brachiaria decumbens, Panicum maximum cv. Massai and, Andropogon gayanus.).The P. maximum cv. Massai grass presented higher (P<0.05) protein content (7.4%) than B. humidicola and A. gayanus (3.3 and 3.6, respectively), whereas the NFD, AFD, cellulose and lignin contents didn’t differ among grasses. The content of hemicellulose was lower in P. maximum cv. Massai, B. decumbens and A. gayanus grasses. Higher values of DM disappearance of tropical grasses were found in 96 hours (mean value 36.16, 55.52 and 80.20% for 6, 24 and 96 h, respectively) . B. decumbens had higher values of effective digestibility(ED) in three passage rates (PR): 67.7, 57.1 and 51.3% in PR of 2, 5 and 8%, respectively. B. humidicula and P. maximum cv. Massai grasses had the lowest potential degradability, 78.9% and 77.6%, respectively. The nonlinear model was adjusted satisfactorily to data from DM. The coefficients of determination (R2) obtained for the curves of degradability in both for age degradability were greater than 93%.
Keywords: Andropogon gayanus, Brachiaria spp., Panicum maximum