APPLICATION OF FECAL NIRS PROFILING TO PREDICT DIET CHARACTERISTICS AND VOLUNTARY INTAKE IN BEEF CATTLE

Abstract Text:

Objectives of this study were to evaluate the use of fecal near-infrared reflectance spectroscopy (fecal NIRS) to predict dietary characteristics and voluntary DMI in beef cattle. Fecal samples and phenotype data were collected from 11 growing cattle trials for which intake was measured individually (Calan-gate or GrowSafe systems), and residual feed intake (RFI) calculated. For each trial, animals were fed diets containing at least 70% roughages (1.9 to 2.7 Mcal ME/kg DM), and composite fecal samples were analyzed using a Foss NIRS 6500 monochromator. Modified partial least squares approach was used to develop calibration equations to predict CP, NDF, and DMI using fecal NIRS spectra as independent variables, and CP, NDF, or DMI as dependent variables. Calibration accuracies (SE calibration; SEC and R² of calibration; R²_c) were 0.61 and 0.90 for prediction of CP, 2.35 and 0.85 for NDF, and 11.3 and 0.76 for DMI. Validation of equations was accomplished by cross-validation, and evaluated using SE cross-validation (SECV) and R² of cross-validation (R²_cv). Validation accuracies (SECV and R²_cv) for prediction of CP and NDF were acceptable and in agreement with previous studies, further indicating that fecal NIRS is a capable tool for predicting dietary CP and NDF. Validation accuracy for prediction of DMI was less accurate than for prediction of dietary CP and NDF. However, the results were comparable to those reported for the prediction of individual-animal intake by fecal NIRS and n-alkane methods in previous studies. Additionally, the fecal NIRS prediction equation for DMI in this study was able to predict individual-animal DMI for the evaluation of divergent RFI groups. Across studies, low RFI animals consumed 12% less (P < 0.01) than high RFI animals based on observed intakes (107.8 vs. 122.4 ± 2.2 g/BW^0.75), and 10% less (P < 0.01) based on fecal NIRS predicted intakes (108.9 vs. 120.9 ± 2.13 g/BW^0.75). Results from this study indicate that fecal NIRS profiling may be useful in predicting animal variance in diet characteristics and DMI.

Table 1. Statistical performances of fecal NIRS calibrations.

Item	N	Outliers1	Mean	SEL2	Calibration			Validation
					SEC	R2c		SECV	R2cv
CP, % DM	408	22	13.14	0.10	0.61	0.90		0.67	0.88
NDF, % DM	408	15	55.21	0.31	2.35	0.85		2.46	0.82
DMI, g/BW0.75	408	20	109.1	1.18	11.3	0.76		11.8	0.73
1Identified by “GH” statistic ≥ 8.0 or “T” statistic ≥ 2.5. 2 SEL: SE laboratory.

Keywords:

beef cattle, fecal NIRS, feed intake