Requerimentos nutricionais de cordeiros Santa Inês com peso corporal de 14 A 28 kg

Abstract

The objective of this study was to determine the body composition, the net energy and protein requirements for maintenance and weight gain, the efficiency of utilization of metabolizable energy for maintenance and weight gain and the dietary requirements of total digestible nutrients (TDN) and metabolizable protein (MP) of Santa Ines lambs, fed diets containing different levels of metabolizable energy (ME). We also evaluated the Small Ruminant Nutrition System (SRNS) model to predict the dry matter intake (DMI) and the average daily gain (ADG) of Santa Ines lambs. Were used 35 lambs, non-castrated, with initial body weight (BW) averaging 14.77 ± 1.26 kg and about two months of age. For determination of body composition, in accordance with the methodology of comparative slaughter, at the beginning of the experiment, five animals were slaughtered to serve as reference for the estimates of empty body weight (EBW) and initial body composition of the 30 remaining animals, which were distributed in randomized block design with five treatments and six replications. The treatments consisted of diets containing increasing levels of ME (1.13; 1.40; 1.73; 2.22 and 2.60 Mcal/kg DM). When the animals of one of the treatments reached BW average of 28 kg, all the 30 animals were slaughtered. The body content of protein decreased from 218.13 to 183.96 g/kg EBW, while fat and energy increased from 80.70 to 157.49 g/kg EBW and 1.98 to 2.49 Mcal/kg EBW, respectively, with the increase in the BW of the animals from 15 to 30 kg. The net energy requirement for maintenance was 51.93 kcal/kg EBW0.75/day. The net protein requirement for maintenance was 1.34 g/kg BW0.75/day. The demand of net energy for weight gain (NEg) increased with the increase in the BW and in the ADG of the animals. The demand of net protein for weight gain (NPg) decreased with the increase in the BW and increased with ADG of the animals. The efficiency of utilization of metabolizable energy for maintenance (km) was 66%. The average value of efficiency of metabolizable energy utilization for weight gain (kf) was 48%. The dietary requirements of TDN and MP increased with the increase in the BW and in the ADG of the animals. The model SRNS underestimated the DMI and ADG of the animals in 6.2% and 24.6%, respectively. The fat and energy content in the empty body, as well as the requirement of NEg increase, while the protein content for kg of EBW and the NPg requirement decrease with the increase in the BW of the animals. The nutritional requirements of Santa Ines lambs, in general, are lower than those suggested by international systems evaluation of food and nutrient requirements of small ruminants. The model SRNS can be used to predict the DMI of Santa Ines lambs, however, for variable ADG, more studies are needed, since the model underestimated the response of the animals of this study in 24.6%.