Evaluation of the Pampa Corte model for predicting dry matter intake and digestibility by sheep fed tropical forages

Abstract

The aim of this study was to evaluate the adequacy of the Pampa Corte model associated to an in vitro gas technique as a tool for predicting dry matter (DM) intake and digestibility by sheep fed tropical forages. In addition, the adequacy of the Pampa Corte in predicting DM intake was also compared to NRC (2007). Individual data (n = 154) of observed DM intake and digestibility, as well as of body weight and chemical composition of consumed diet, were obtained from ten digestibility trials conducted with male growing wethers housed in metabolic cages and fed ad libitum tropical grasses associated or not with tropical legumes. Individual observations of each variable were averaged by treatment (n = 25) within trials, which were then compared to values predicted by the Pampa Corte or NRC models through concordance correlation coefficient (CCC) and regression analyses. The prediction of DM intake by Pampa Corte resulted in higher CCC (0.95 vs. 0.68) and R2 values (0.92 vs 0.74) than by NRC. Moreover, the slope of the linear regression between observed and predicted values was not different from 1 for Pampa Corte whereas it was lower than 1 for NRC (P < 0.05). The intercept of both linear relationships was not different from 0. Observed values of DM digestibility were linearly related to those predicted by Pampa Corte model (P < 0.05) with a low CCC (i.e. 0.54). In conclusion, the Pampa Corte model was adequate in predicting DM intake by sheep fed tropical forages, showing a better predictive performance than NRC (2007). However, DM digestibility was underpredicted by the Pampa Corte model.