Composição botânica e protéica da pastagem e da dieta e desempenho de bovinos em caatinga nativa manipulada

Abstract

A research was carried out in the period of August 1986 to July 1987 at the Unidade de Execução de Pesquisa (UEP) of Serra Talhada, belonging to Empresa Pernambucana de Pesquisa Agropecuária (IPA), in the microregion 104- Alto Pajeú, with the objective of evaluating the introduction of buffelgrass (Cenchrus ciliaris) cv Gayndah to a caatinga site, in terms of seasonal behaviour of the cattle diets, the diet profile along several times of the year, the stabilization of the forage supply, and of the animal and pasture performance. The native caatinga was manipulated by strip cutting the woody vegetation, followed by reseeding with buffelgrass. Four levels of manipulation were tested, that is, M0 - untouched caatinga, M1 - 50% manipulated, M2 - 75% manipulated and M3 - 100% manipulated. A randomized block design with a 4 x 6 factorial (four levels and six times of the year) with two replications was followed. The vegetation was stratifiedly sampled on the cut and uncut strips, at intervals of two months, by estimating the total phytomass by the double sampling method, as described by CAMPBELL and ARNOLD (1973). The dry matter, crude protein, and the ashes were determined, according to the AOAC (1970) recommendations. Steers with esophageal fistulas were used for diet evaluations, according to LIMA (1976), and the botanical identification of the diet was done by the microscopic point thechnique, as described by HARKER (1964). The preference index by cattle was determined according to HEADY (1975). Animal production was measured, by using 3/4 zebu steers, with a initial live weight of 315.0 kg, on a continous with adjusting stocking rate grazing system. The introduction of buffelgrass at increasing levels resulted on significant (P<0.05) raising and stabilization of grazeable phytomass along the year, with significant (P<0.05) changes on the botanical composition of the pasture, by increasing the participation of the grass components. Cattle selected (P<0.05) grasses, composing up to 91.2% of the diets. The protein content in the diets, apparently was always higher than that in the pasture. And so, the pasture and animal performances were substancially increased, varying the daily average gain from 0.090 to 0.460 kg/head, the animal live weight production from 4.2 to 123.9 kg/ha and the stocking rate from 12.5 to 1.4 ha/ AU, respectively for the areas of native caatinga and 100% manipulated caatinga and reseeding by buffelgrass. It was concluded that the woody species manipulation followed by buffelgrass reseeding constitute a technically recomended practice to the improving the cattle raising system on the caatinga region.