Energy requirements of female sheep at increasing ages and fed at different concentrate levels

This study aimed to estimate the energy requirements of Santa Ines females. Forty Santa Ines females with an average initial body weight (BW) of 16.27 ± 1.44 kg and an age of 150 ± 10 days were used. Four animals were slaughtered on the first day of the experimental period to serve as a baseline group. The remaining 36 females were assigned to a completely randomized design in a factorial arrangement with different concentrate levels [50% concentrate ad libitum(CL1), 25% concentrate ad libitum, and 25% concentrate with restricted intake at 1.9% of body weight (CL2R)] and slaughter ages [200 days (A1), 250 days (A2) and 330 days (A3)]. The net energy requirements for maintenance (NEm) were estimated through regression analysis of heat production (HP) on metabolizable energy intake (MEI). The net energy requirements for gain (NEg) were estimated by regressing retained energy (RE) on empty body weight gain (EBWG). Energy concentration of gain increased with age (P = 0.053), and was higher (P = 0.021) in females fed a 50% concentrate diet. The NEm was estimated at 0.077 Mcal/kg0.75EBW/day. The model generated for NEgwas 0.4489 × EBW0.75 × EBWG1.0284. The energy requirements of Santa Ines females remain constant up to 330 days of age.