Range management and cow´s consumption of Trichloris crinita

Abstract

The continuous use of the livestock fields of the Middle Valley of Rio Negro, North Patagonia, Argentina is causing rangeland degradation. Cattle breeding using rotation regimes between plots of known vegetations composition in a valley field, with 303 mm as historical annual rainfall, was planed to evaluate the population of Trichloris crinita, a native to the Americas known by the common name false Rhodes grass, and to estimate its consumption and preference by cows. To describe floristic composition, the identification of plant species was made on intercepting lines. The diet of grazing animals was determined by microhistological studies using the epidermal characteristics to identify plant components in cows´ fecal samples. Plots at the bottom edge of the plateau that surrounds the valley, with alluvial soils and little biodiversity, where T. crinita grows spontaneously, were left free of animals during the summer and autumn period, allowing the vegetative and reproductive development of the species. The use of this forage in winter as deferred pasture permitted the increase of T. crinita population, with higher annual dry matter production per plant and resulted in an enhanced cows´ consumption.