Application of Near Infrared Reflectance Spectroscopy to Predict Fecal Composition and Its Use for Digestibility Estimation

Abstract

Two experiments were carried out to investigate the applicability of near infrared reflectance spectroscopy (NIRS) to predict the chemical composition of feces. and thereby to estimate digestibility based on a lignin indicator method. Ninety five fecal samples collected from digestion trials using dairy cattle were SUbjected to NIRS for the prediction of chemical composition. Three methods to determine feed digestibility were compared. namely by digestion trial (in vivo). by the lignin indicator method using data from chemical analysis (LiGLab). and by the lignin indicator method from NIRS prediction (LIGNIR). DigestIbility was evaluated for three groups of feeds based on the type of feedstuff used in the ration. The groups were italian ryegrass only (lRO, n 20). Italian ryegrass-concentrate ration (IRCT, n = 16). and Italian ryegrass -steamed wood ration (IRSW, n =12). The rations were adjusted so as to meet the total digestible nutrients requirement of the Japanese Feeding Standard. This study showed that fecal compo· sition could be accurately predicted by NIRS. The values obtained by the NIRS prediction method for unknown samples and the respective values obtained by chemical analysis were highly correlated for acid detergent fiber, crude fiber, lignin and ether extract; the correlation coefficients (r) were 0,98, 0.98, 0,97 and 0.96, respectively. Correlation coefficients for crude protein, organic matter and energy were 0.91, 0.91 and 0.82, respectively. With respect to digestibility estimation, the value for the L1GLab and LIGNIR estimations and that for the in vivo were very similar. The difference between the LIGLab and LIGNlR values and the in vivo value was below 3%, the standard deviation of difference was less than 5%, The results show that digestibility estimation using lignin determined by NIRS as an indicator was useful for the routine evaluation of nutritive values because it is simple, fast and accurate, Anim. Sci. Technol, (Jpn.) 67 (10) .' 851-861, 1996 Key words: NIRS, Fecal composition, Lignin, Digestibility, Dairy cattle