Evaluation of Feed Near-Infrared Reflectance Spectra as Predictors of Methane Emissions from Ruminants.

Feed chemical composition is associated with methane (CH 4 ) formation in the rumen, and thus CH 4 yields (Y m ; CH 4 emitted from per unit of dry matter intake) could be predicted using near-infrared reflectance spectroscopy (NIRS) of feeds fed to ruminants. Two databases of NIRS data were compiled from feeds used in experiments in which CH 4 yields had been quantified in respiration chambers. Each record in the databases represented a batch of feed offered to a group of experimental animals and the mean CH 4 yield for the group. A near-infrared reflectance spectrum was obtained from each feed, and these spectra were used to generate a predictive equation for Y m . The predictive model generated from brassica crops and pasture fed at a similar feeding level ( n = 40 records) explained 53% of the variation in Y m and had a reasonably good agreement (concordance correlation coefficient of 0.77). The predictive ability of the NIRS calibration could be useful for screening purposes, particularly for predicting the potential Y m of multiple feeds or feed samples, rather than measuring Y m in animal experiments at high expenses. It is recommended that the databases for NIRS calibrations are expanded by collecting feed information from future experiments in which methane emissions are measured, using alternative algorithms and combining other techniques, such as terahertz time-domain spectroscopy.