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
Highlights
Livestock production in semi-arid Brazil is based on Caatinga rangeland (Araújo Filho et al 1998), which covers approximately 86% (83.5 Mha) of the region (3‒16° S, 35‒45° W) and 9.8% of Brazil’s land area (IBGE 2012)
The objective of this study was to document the seasonal changes in botanical composition of available forage and the diets selected by sheep continuously grazing partially cleared Caatinga over-seeded with perennial grasses
Factors such as the irregularity of rainfall and reduced forage mass can promote change in the botanical composition of the pasture and increase bare soil, which may contribute to the persistence of species with low forage value and less selected by animals (Tothill 1987)
Summary
Livestock production in semi-arid Brazil is based on Caatinga rangeland (Araújo Filho et al 1998), which covers approximately 86% (83.5 Mha) of the region (3‒16° S, 35‒45° W) and 9.8% of Brazil’s land area (IBGE 2012). The upper story of shrubs, small trees and prickly deciduous vegetation consists mostly of Leguminosae, Euphorbiaceae, Cactaceae and Bromeliaceae, while the herbaceous layer is comprised primarily of annual grasses and dicotyledons. The majority of this vegetation has low forage value and the upper story is partially inaccessible to sheep (Santos et al 2010). To improve management of the Caatinga, studies of ecosystems should determine botanical composition, forage mass and nutritive value as well as soil characteristics (Heady 1975; Holechek et al 2006; Albuquerque et al 2008). This information will help land managers better understand soil-plant-animal-environment interrelationships and develop productive and sustainable management strategies
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