Exigências de energia e proteína para mantença e ganho em ovinos morada nova de diferentes classes sexuais em confinamento.

Abstract

This study estimated the energy and protein requirements of intact male, castrated male and female Morada Nova lambs. The animals were distributed in completely randomized design in a factorial treatment structure of 3 x 3 with three sexes (15 intact males, 16 castrated males and 16 females) and three levels of restriction (ad libitum, 30 and 60%) with an initial body weight (iBW) of 14.50 ± 0.89 kg. Four animals of each sex class were slaughtered at the beginning of the experimental trial as the reference group for initial body weight and empty body weight estimation (EBW). When the experimental test reached 120 days all the animals were slaughtered. The proportions of fat, protein, ash and water (% EBW) were not influenced (P > 0.05) by the different sexual classes. The net requirement of energy for maintenance (NEm) was equal (P = 0.1704) between sexes at 73.0 kcal/kg EBW0.75/day with an efficiency of utilization of energy for maintenance (km) of 58%. The net energy for gain (NEg) was different (P < 0.0001) between the sexes. For animals weighing 15 kg and that had an average daily gain of 200 g, the NEg was 0.297; 0.304 and 0.411 Mcal/kg EBW0.75/day for intact males, castrated males and females, respectively. The net energy requirement for gain in females was 26% higher than in intact males and castrated males. The energy utilization efficiency for weight gain (kg) was different (P < 0.0001) between the sexual classes: 32, 27 and 29% for intact males, castrated males and females, respectively. There was no difference (P = 0.7783) between sexes for the required net protein for maintenance (NPm) and that amount was 1.06 g/kg BW0.75/day. A value of 3.46 g/kg BW0.75/day was estimated for metabolizable protein maintenance requirements (MPm). The net protein requirement for weight gain (NPg) was influenced (P < 0.001) by the sexual classes and decreased according to the increase in BW. The efficiency of use of the protein for weight gain (kpg) was different (P < 0.0001) between the sexes, being 28, 18 and 15% for intact males, castrated males and females, respectively. Sex did not affect the maintenance energy or the protein net requirement for lambs to grow. The net requirements of energy gain increase and protein requirements decrease with the increase in body weight of lambs.