Botanical composition and nutritional value of natural pasture of the Caatinga selected by sheep receiving different amounts of an energy-protein supplement

Abstract This study aimed to evaluate the composition and nutritional value of the diet selected by sheep on Caatinga pasture receiving different amounts of concentrate supplementation. Thirty-two sheep were divided into four groups (0g; 200g; 350g and 500g of supplementation per day), on native Caatinga pasture, during the rainy, transition and dry seasons, from 2015 to 2017. An inventory was carried out and samples of the species present in the pasture were collected to prepare microscopic slides. To identify the selected diet, samples of feces were collected and the slides were prepared and examined. Based on the frequency of species observed in the slide readings and the nutritional value determined in the bromatological analysis, it was possible to determine the key species and the quality of the selected diet. There was no effect of interaction between the level of supplementation offered and the season (P > 0.05). Sheep supplemented with 500g concentrate⁻ ¹ day⁻ ¹ had higher preference for herbs and other dicotyledons and less selection for grasses. Of the 63 species catalogued in the caatinga pasture evaluated, the fecal micro-histological technique allowed the identification of 26 species in the botanical composition of the diet, 20 of which were highly preferred and 7 were considered key species: Stylosanthes humilis and Cynodon dactylonin the rainy season, Aristida longiseta, Mimosa caesalpinifolia, Herissanta tiubae and Commelina diffusa in the transition, and Aristida adscensionis and Mimosa caesalpinifolia in the dry season. Sheep managed on native Caatinga pasture change their selection strategy according to the supplementation they are offered.