The voluntary forage intake and nutrition of goats and sheep in the semi-arid tropics of northeastern Brazil.

The nutritive value of diets selected by free-ranging goats and sheep, and estimates of forage intake, were obtained during the wet (January to May, 1982) and the dry season (June to December, 1981) in the Brazilian state of Ceara. Esophageally fistulated animals were used to collect dietary samples for nutritive evaluation. Organic matter intake (OMI) was estimated by total fecal collections. Goats selected diets higher in crude protein (CP) than did sheep (16.3 and 15.5%, respectively; P = .03). Contrary to current hypotheses, goats did not generally select diets of higher nutritional quality than did sheep. Sheep diets had lower (P less than .05) levels of lignin and equal (P greater than .1) levels of cell wall fiber compared with goats' diets. No difference in in vitro organic matter digestibility (IVOMD) was found between sheep and goats (P greater than .1), averaging 54%. However, major differences in IVOMD occurred during the wet season, as sheep diets were 4 to 10 digestibility units higher than were goats' diets. This may have been due to problems in using the in vitro procedure for dietary samples high in browse material. The OMI averaged 2.2 and 2.1% of body weight for sheep and goats, respectively (P = .08). Lowest levels of OMI (1.2% for sheep and goats) were noted during the latter portion of the wet season when forage biomass was high but nutrient quality was declining due to maturation. Daily digestible energy (DE) intake (kcal) differed (P = .04) between sheep (1,665.5 +/- 23.7) and goats (1,329.7 +/- 27.5).(ABSTRACT TRUNCATED AT 250 WORDS)