Application of fecal near-infrared reflectance spectroscopy profiling for the prediction of diet nutritional characteristics and voluntary intake in beef cattle

The objective of this study was to evaluate the use of fecal near-infrared reflectance spectroscopy (NIRS) profiling to predict diet nutritional characteristics and voluntary DMI in beef cattle. Fecal samples were collected for growing cattle across 11 experiments in which individual animal performance and DMI was measured. Dried and ground fecal composite samples collected from each animal were subjected to fecal NIRS analysis by a Foss NIRS 6500 scanning mono-chromator (Foss, Eden Prairie, MN) at the Grazingland Animal Nutrition Laboratory (Temple, TX). Fecal spectra were then used to develop equations to predict diet composition (trials 1 to 11; n = 408), digestibility (tri-als 1 to 5; n = 155), and DMI (trials 1 to 11; n = 408). Coefficients of determination for calibration (R²_c) and cross-validation (R²_cv) for prediction of diet nutritional characteristics were lower for NDF (R²_c = 0.85; R²_cv = 0.82) than for CP (R²_c = 0.90; R²_cv = 0.88). For the prediction of DMI, R²_c and R²_cv ranged from 0.69 and 0.67 for the prediction of trial-average DMI to 0.76 and 0.73 for the prediction of fecal-collection-period DMI. While the R²_c and R²_cv obtained for the prediction of DMI were lower than those obtained for the prediction of diet composition or digestibility, fecal NIRS prediction equations for DMI were successful in predicting the mean DMI of groups, as no differences were found for the prediction of fecal-collection-period DMI (Diff. = 1.10; P = 0.72) or trial DMI (Diff. = -0.47; P = 0.86).