Joint vis-NIRS evaluation of feeds and dried feces to estimate ingestion and digestibility in growing rabbits.

A group of 51 feed samples taken from 12 experimental diets and of 66 dried grouped feces belonging to four nutrition experiments were submitted to a Uv-VIS-NIRS scan (350-2500 nm) in order to calibrate the chemical composition and nutritional parameters, that is namely, the ingestion aptitude and digestibility. A new chemometric system has made it possible to contemporary use the spectrum of the diet together with the spectra of the relative pool of dried feces. The daily measured ingestion, in absolute as the intake and in relative, as the palatability per unit of metabolic weight, obtained a good resolution for the spectra of the feeds (R2cv= 0.80 and 0.75, respectively), for the feces (0.81 and 0.80) and for the joint evaluation (0.87 and 0.81). The intake was positively correlated to the mineral, insoluble ash, protein, gross energy, crude fiber and acid detergent fiber (ADF) in the feeds, and negatively correlated to N-free extract, lignocellulose and to all the digestibility coefficients except crude fiber. Very significant improvements, on the average of some 0.20 absolute R2 points, corresponding to 87% as relative, were also provided to the digestibility coefficients by the joint method; in decreasing order: neutral detergent fiber (R2cv= 0.00; 0.18 and 0.50, respectively, for the feeds, feces and joint: +41% vs. the average of feeds and feces), ADF ( 0.00; 0.45 and 0.62: + 39%), ether extract (0.53; 0.52; and 0.86: +34%), crude protein (0.53;0.53 and 0.75: +22%), gross energy (0.61; 0.74 and 0.83: +15%), crude fiber (0.61; 0.82 and 0.82: +11%), dry matter (0.60; 0.79 and 0.76: +7%), organic matter (0.65; 0.80 and 0.79: +6%) and the N-free extract (0.86; 0.82 and 0.87: +3%). The results corroborate previous knowledge and show the possibilities of using NIRS fecal profiling in rabbit nutrition, which joined together with NIRS of the feeds, could optimize nitrogen monitoring.