Exigências nutricionais de energia e proteína para ganho de peso em ovinos e caprinos

Abstract

Although goats and sheep are often raised together in Brazil, their physiological and metabolic characteristics may entail distinct nutritional requirements, which remain largely unexplained, especially considering that the main feeding systems were developed based on data from temperate regions and breeds other than tropical ones. Therefore, the goal of this study was to determine the nutritional requirements of energy and protein for body weight gain in entire male Santa Inês sheep and Boer goats. Thirty animals were used, consisting of 15 male Santa Inês sheep and 15 male Boer goats, with an average initial body weight of 24 kg ± 3.5 kg. On the first day of the experimental trial, according to the comparative slaughter methodology, six animals were randomly selected from each species and slaughtered to serve as a reference group for estimating initial EBW and initial BC. The remaining 24 animals were distributed in a randomized design in a 3×2 factorial arrangement with three dietary levels (ad libitum, 30% and 60% feed restriction) and two species. At the end of the experimental period, after 180 days, the remaining animals were slaughtered. The net energy requirements for gain (NEg Mcal/day) were estimated by regression of retained energy against metabolic empty body weight (EBW0.75) and empty body weight gain (EBWG). No significant effect of species (P > 0.9309), was observed, obtaining a single equation for both species: NEg (Mcal/day) = 0.213(±0.06523) x EBW0.75 x EBW0.8874(±0.05648). The net protein requirement for gain (NPg g/day) was determined based on the logarithmic equation: Log Protein: 2.19 (± 0.069) + 0.985 (± 0.046) x Log EBW, also with no significant effect of species (P > 0.1614), allowing the estimation of NPg (g/day) through a single general equation for goats and sheep. From the NEg (Mcal/day) equation generated in this study, entire male sheep and goats ranging from 10 kg to 40 kg BW and an ADG of 0.100 kg/day obtained the same values of 0.092 Mcal/day and 0.318 Mcal/day, respectively. Based on the NPg equation, the net protein requirement for gain ranged from 12.89 to 24.84 g/day for sheep and from 13.93 to 25.85 g/day for goats, considering weights from 10 to 40 kg and ADG of 0.100 to 0.200 kg/day, respectively. Therefore, the energy and protein requirements for weight gain did not differ for the two species.