Dietetic requirements and evaluation of a small ruminant nutrition system model in Morada Nova lambs

This study was carried out to estimate efficiencies of the utilization of metabolizable energy for maintenance (km) and weight gain (kg) and to evaluate the Small Ruminant Nutrition System (SRNS) model in predicting dry matter intake (DMI) and average daily gain (ADG) of growing Morada Nova lambs. The animals were non-castrated and two months of age, with initial body weights averaging 12.05 ± 1.81 kg. Eight animals were slaughtered at the beginning of the trial as a reference group, in order to estimate initial empty body weight and body composition. The remaining animals were assigned to a randomized block design with eight replications per block and five diets with increasing metabolizable energy levels (0.96, 1.28, 1.72, 2.18 and 2.62 Mcal/kg of dry matter (DM)). The metabolizable energy use efficiencies for maintenance and for weight gain were calculated from the relationship between the dietary net energy for maintenance and gain and ME concentration in the diets. Evaluation of the SRNS model was performed by adjustment of simple linear regression model between the predicted (independent variable) and observed (dependent variable) values. The efficiency of ME utilization for maintenance (0.96 Mcal/kg DM) was 0.24 and decreased (0.60 to 0.40) for the other treatments with increasing energy content. The DMI and ADG predicted by the SRNS model did not differ (P?0.05) from the observed values. Thus, the SRNS model can be used to estimate the DMI and ADG in feedlot Morada Nova lambs.