Prediction of energy requirement for growing sheep with the cornell net carbohydrate and protein system
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This study evaluates the suitability of the Cornell Net Carbohydrate Protein System for sheep (CNCPS-S) to predict average daily gain (ADG) of lambs. This model was also used to compare the efficiency of use of metabolizable energy (ME) to net energy (NE) for growth (kg) from the Agricultural Research Council (ARC, 1980), the Australian system (CSIRO, 1990), the National Research Council (NRC, 2000) and a theoretical equation by Tedeschi et al. (2004), which uses a decay equation as a function of the composition of the gain. In addition, the equations used by ARC (1980), NRC (1985) CSIRO (1990) to predict the energy content of empty body gain (EVG) were compared. Forty-two data points from nine published studies were used to investigate the adequacy of CNCPS-S of the above equations to estimate ADG. Regardless of the kg prediction equation used, the CNCPS-S markedly underpredicted ADG, due to an overprediction of ME requirements for maintenance (MEm). When the factors causing overprediction of MEm were corrected, the CNCPS-Sunderpredicted ADG when the NRC (1985) CSIRO (1990) equations were used to estimate kg, while good precision accuracy were achieved when kg was predicted with the Tedeschi et al. (2004) ARC (1980) equations. With the ARC (1980) equation, the CNCPS-S model explained 82% of the variation in ADG, with small mean bias (-4 g/day) root mean squared predicted error (RMSPE) (40 g/day); the simultaneous test of the intercept slope did not reject (P > 0.1) the hypothesis that they were statistically similar from zero unity, respectively. The model had an accuracy of 0.90 when evaluated with the concordance correlation coefficient test. The comparison of three different equations to predict EVG indicated that the best CNCPS-S prediction of ADG was obtained with the CSIRO (1990) approach.We concluded that a modified CNCPS-S model can be used to accurately predict ADG of growing lambs. CAB International 2006.