Exigências de proteína e energia para caprinos moxotó em crescimento

Abstract

Twenty-six Moxotó non-castrated male kids (averaging 15 kg of initial body weight (BW) and 6-8 months old ) fed a diet with 2.6 Mcal of metabolizable energy were used to evaluate the body composition and energy and protein requirements for weight gain and to predict the net energy requirements for maintenance and net efficiency of metabolizable energy utilization (EMEU) for maintenance (km) and weight gain (kf). At the beginning of the experiment, six animals were slaughtered as reference to estimate initial body composition and initial empty body weight (EBW). Afterwards, five groups of four animals (one for each intake level) were assigned to complete randomized design, in the following treatments: 100% or ad libitum (AL), 85, 70 and 55% of ad libitum. Each group was slaughtered when BW of AL animals reached 25 kg BW. Logarithm equations of body contents of fat (BCF), energy (BCE) and protein (BCP) were fitted on log10 of empty body weight (EBW). By differentiation of those equations, the prediction equations of BCF, BCE and BCP per kg of EBW gain were obtained. The net energy requirements for maintenance were estimated by the logarithm or exponential rela tions of heat production (HP) andmetabolizable energy intake. Estimates of kf and km were calculated as the relation of dietary net energy for gain and maintenance, respectively, and the dietary ME concentration. After, ME and TDN requirements were estimated. Low body water concentration was observed in the experimental animals, but the depositions of fat, protein and ash increased with maturity. Increasing BCF (from 78.55 to 125.38 g/kg of EBW) and BCE (from 1.90 to 2.34 Mcal/kg of EBW) were obtained when animal BWincreased from 15 to 25 kg. Positive linear relation between energy composition in EBW gain (EBWG) (Mcal/kg) and EBW was observed. Similar response was evident for fat contents in gain. Contents of BCF (g) and BCE (Mcal) contents of Moxotó kids increased from 14.33 to 22.87 and from 0.26 to 0.32 per 100 kg of EBWG, respectively, as EBW increased. The protein contents remained constant and ranged from 205.60 to 201.69 g/kg of EBW, and it was observed reduction of 1.9% as BW increased from 15 to 25 kg. Although small body change of net protein requirements was observed in the experimental animals as BW increased, the fat:protein ratio increased as BW increased. To convert the EBW requirements into BW, it is recommended to use the corrected equation. The net energy requirement for maintenance of 55.11 kcal per kg EBW0.75 was next to the predicted by the North American report for this specie. This value is considered low if compared to that reported in the Brazilian literature, possibly, due to the fact of these animals had developed mechanism of low basal metabolism. Km estimate was of 0.57. Kf estimates were of 0.22, 0.19, 0.28, and 0.36, respectively, for the concentrations of 2.99, 2.95, 2.56 e 2.5 Mcal/kg of dry mater