Botanical composition of Caatinga rangeland and diets selected by grazing sheep

Abstract

Sheep dietary selection from species-diverse Caatinga rangeland of semi-arid northeastern Brazil has not been documented. This study examined the botanical composition of the available forage and diets of Dorper x Saint Ines ewes on thinned Caatinga over-seeded with Cenchrus ciliaris and Urochloa mosambicensis. Sixty-three species from 23 families, dominated by shrubs and short trees of low forage nutritive value, were identified in the vegetation. The botanical composition revealed, on average, high presence of 29.2% Malvaceae and 13.0% C. ciliaris. Using the microhistological technique, sheep showed, on average, 59.6% preference for dicotyledons throughout the year. However, selectivity indexes indicated, on average, greater selection for Poaceae during the rainy season (1.5) and for dicotyledons in the dry season (1.8) with a year-round aversion for Malvaceae (0.3). These findings suggest that Caatinga vegetation management should include Malvaceae thinning and greater incorporation of grasses and herbaceous legumes to improve rangeland carrying capacity. Keywords: Brazil, continuous stocking, dietary selection, microhistological technique, principal components.DOI: 10.17138/TGFT(4)71-81