Comparative studies of Eragrostis plana (Annonigrass) and lowland native pasture in the area of Santa Maria, Rio Grande do Sul, Brazil. I. Chemical Characterization

Abstract

An experimental area of 12.000 m², belonging to the Department of Zootecnia, Federal University of Santa Maria, Brazil, was used for this study. Half of this area was in Eragrostis plana Nees (annonigrass), and the remainder in lowland native pasture. Following burning and mechanical clipping, two areas measuring 144 m² were used in each pasture, and each area subdivided into 12 plots of 3 x 4 m each. Beginning in September, two plots from each area were cut each month until all plots had been cut (12 months); three months after each cutting, each plot was again cut. Samples of each cutting were analysed for dry matter, crude protein, ether extract, crude fiber and ash, as well as in vitro digestibility. Inasmuch as first cuttings were concerned, marked decreases in crude protein content were noted for both pastures, with that in case of E. plana having a more pronounced decrease than pasture, with increasing maturity. Crude fiber content of annonigrass was always greater than that of native pasture. The 90-day-old cuttings favored native pasture in terms of crude protein (higher) and crude fiber (lower) content. Native pasture was always considerably higher in ash. In vitro dry matter digestibility results of the first cutting were higher for annonigrass, however a fester decrease in this measure was observed for the annonigrass than for native pasture; furthermore, the possibility of organic matter digestibility showing more favorable results for native pasture is desired. These results place doubts upon the analytical feeding value of annonigrass as a substitute for native pasture in the state of Rio Grande do Sul, principally when it is considered that sample of native pasture used as a comparison for annonigrass in this study is typically of low quality and considerably inferior to predominating native pasture in well-drained areas.