Evaluating NIRS for predicting faecal fibre, protein fractions and digestibility in dairy sheep and goats fed alfalfa hay and concentrate

This study evaluated the effectiveness of near-infrared spectroscopy (NIRS) in predictingfaecal fibre, protein fractions and total tract apparent digestibility in dairy sheep and goats fedvarying ratios of alfalfa-hay and concentrate. A total of 180 faecal samples from dairy sheep andgoats were collected and chemically analysed. Faecal samples underwent also NIRS spectralacquisition and calibration models were obtained through modified partial least square regres-sion and tested for robustness. The NIRS provided excellent estimations for N and CP as % as is(R2ExV 0.91 and 0.91, RPD 3.16 and 3.33, respectively), good estimation for N, CP and ND solubleCP % DM (R2ExV 0.90, 0.90 and 0.85, RPD 3.14, 2.90 and 2.48) and ND soluble CP expressed as %as is (R2ExV 0.87, RPD 2.55), approximative quantitative prediction for acid detergent insolublecrude protein (ADICP) and ADIN % acid detergent fibre (ADF) (R2ExV 0.79 and 0.71, RPD 1.93and 1.78, respectively) and ADICP as % as is (R2ExV 0.67, RPD 1.70) but resulted to be less effect-ive when predicting all the other components. The prediction models for total-tract digestibility(ttD) of ADICP performed best among the developed equations (R2ExV 0.57, RPD 1.38), but themodel was not sufficient for precise predictions, suggesting a good capacity of NIRS to predictfaecal N excretion but also intrinsic limitations of faecal spectra due to the partial residualnutrients content, compared to the diet. Increasing the number of calibration samples and val-ues, the forage species, and the F:C ratios in the diet offered to the animals could improve theNIRS performance