The high cost of raw materials has contributed to manage feed as closely as possible to the requirements of animals. It is essential to know precisely the nutritional value of resources and to adapt the formulation matrices to the actual price of these resources. The measurements of digestibility are key parameters in the evaluation of feeds; however, the measurements on animals require heavy experimental trials, high cost of in vivo experiments and high cost of analysis in the lab, which are hardly feasible when large numbers of determinations are required. The present experiment aimed to investigate the possibility to predict digestibility from NIRS spectra measured on faeces. A total of 200 digestibility collections were carried out on 20 castrated male pigs. Those samples were available from a digestibility experiment investigating the effects of age and genetic background of Large White pigs fed the same diet, rich in fibre (NDF = 21.4% DM) in order to maximize potential digestibility differences between boar origins and their variations with body weight (BW) increase. Digestibility of dry matter (dDM), organic matter (dOM), nitrogen content (dN), energy (dE) and apparent digestible energy content (ADE) were calculated, as well as total N content of faeces (N). The faecal samples were submitted to reflectance NIRS analysis after freeze-drying and grinding.
There was a significant effect of the age of the animals (P<0.001 for all parameters) and of the boar origin (P<0.01 for all parameters, except P=0.025 for dN). Calibration errors and validation errors were, respectively, 0.08% and 0.13% DM for total N in faeces, 0.97% and 1.08% for dDM, 0.79% and 1.04% for dOM, 1.04% and 1.47% for dN, 0.87% and 1.12% for dE and 167 and 213 kJ/kg DM for ADE.
These results indicate that NIRS can account for digestibility differences due to animal factors, with an acceptable accuracy. NIRS appears to be a promising tool for large-scale evaluations of digestibility. It could also be used for the study of digestibility of different feeds, after appropriate calibration based on a wide range of feed types.
Bastianelli, D., Bonnal, L., Jaguelin-Peyraud, Y. and Noblet, J. 2015. Predicting feed digestibility from NIRS analysis of pig faeces. Animal, 9 (5): 781-786. DOI: 10.1017/S1751731114003097