Exigências nutricionais de ovinos mestiços Santa Inês em confinamento.

Abstract

We aimed at determining the energy and protein requirements for maintenance and weight gain of growing Santa Inês crossbreed sheep and, in addition to that, we estimated their fasting body weight and empty body weight (EBW) as a function of their fed body weight. We used data from three comparative slaughtering experiments performed with 150 castrated feedlot sheep, all having similar age and body weight (BW) (20.74 ± 2.99 kg). We tested three models in order to estimate the empty body weight (EBW) based on the fasting BW (FBW) and measured the losses during fasting. The models were: linear, linear with intercept and nonlinear. We estimated the net energy requirements for maintenance (NEm), metabolizable energy for maintenance (MEm), net energy for weight gain (NEg), efficiency at the usage of metabolizable energy for weight gain (Santos et al.), metabolizable protein requirements for maintenance (MPm) and net protein for weight gain (NPg) and efficiency at the usage of metabolizable protein for weight gain (k). The losses during fasting corresponded to 6.18% BW and the relation between FBW and EBW was nonlinear. The NEm and MEm were 70.44 and 109.34 kcal/kg EBW0,75/day, respectively. For NEg, the set up model was based on the retained energy relation as a function of the EBW and the target empty body weight gain. Considering two sheep whose weight were 15 kg and 30 kg with a weight gain of 100 g/day, the NEg is 181 and 360 kcal/kg EBW0.75/day, respectively. The efficiency at the usage of metabolizable energy was 0.41. For MPm, we estimated the value 3.19 g/kg EBW0.75/day. The NPg was 13.13 and 13.61g/day for the 15 kg and 30 kg animals (live weight), respectively, with the same rate of gain, which corresponds to a protein concentration at gain of 170.06 and 160.54 g/kg EBW gain, respectively, and efficiency at the usage of metabolizable protein for gain varying from 0.66 to 0.41. The conclusions are that both MPm and MEm match international recommendations, the net protein requirements per kilogram of weight gain were reduced and the net energy requirements increase with the body weight, and the MPt and MEt increased with the animal’s weight.