RESUMEN
The aim of this study was to determine the energy and protein requirements of non-descript breed hair lambs (NDB) reared under Brazilian semiarid conditions. Sixty animals from three sex classes (20 intact males, 20 castrated males, and 20 females) with an average initial body weight of 18.1 ± 0.4 kg and an average age of 5 months were used. The nutritional requirements were estimated using the comparative slaughter. The animals in the final slaughter group were distributed in a completely randomized design with a 3 × 3 factorial scheme (three sex classes and three feeding levels: ad libitum feeding (positive energy balance), 70% feed restriction (maintenance level), and 80% feed restriction (negative energy balance)). The net energy requirement for maintenance (NEm) did not differ between sex classes (P > 0.05) and it was 68 kcal/kg of metabolic empty body weight (EBW(0.75))/day (P < 0.05). The coefficients for the nonlinear regression of retained energy (RE) on the empty body weight gain (EBWG) were not different among the different sex classes (P > 0.05). The net energy requirement for weight gain (NEg) was estimated by NEg (Mcal/day) = 0.29 × EBW(0.75) × EBWG(0.86) for all sex classes (P < 0.05). The net protein requirement for weight gain (NPg) was estimated by NPg (g/day) = 224.45 × EBWG - 0.025 × RE for all sex classes (P < 0.05). The NEg increased and the NPg decreased with the increase in body weight of NDB lambs.
Asunto(s)
Alimentación Animal/análisis , Proteínas en la Dieta/administración & dosificación , Ingestión de Energía/fisiología , Metabolismo Energético/fisiología , Necesidades Nutricionales , Ovinos/fisiología , Fenómenos Fisiológicos Nutricionales de los Animales , Animales , Composición Corporal , Brasil , Dieta/veterinaria , Proteínas en la Dieta/análisis , Femenino , Masculino , Orquiectomía , Ovinos/genética , Aumento de PesoRESUMEN
The effect of different feeding levels (ad libitum, 25 and 50 % restriction) and genotypes (½ Boer × ½ nondescript breed goats, Canindé, and Moxotó) on carcass quantitative characteristics and non-carcass components (NCC) were evaluated. Forty-five intact male goats were distributed in a 3 × 3 factorial design with five replicates. There was no effect of genotype on carcass weights and yields and retail cuts weights and yields (P > 0.05). Compared to Moxotó, ½ Boer presented better carcass conformation and higher weights (P < 0.01) and yields of viscera from gastrointestinal tract (P < 0.05), and compared to the other genotypes (P < 0.01), ½ Boer presented larger carcass compactness. Carcass weights and yields, retail cuts weights and NCC, and soft tissues yields were higher (P < 0.01) in goats fed ad libitum. The two restriction levels did not differ (P > 0.05) for these variables. There were interactions of genotype and feeding level. At ad libitum feeding, ½ Boer had higher weights of breast and shank, leg, soft tissues, and gastrointestinal viscera compared to the Moxotó (P < 0.05). The crossing of nondescript breed goats with Boer may be a strategy for increasing the efficiency of goat meat production in the Brazilian semiarid. Moreover, in times of feed scarcity, farmers may use higher feed restriction levels to keep animals, since for most of the parameters evaluated, there were no differences between the restriction levels.