Variation among individual beef cattle in methane-to-carbon dioxide ratio measured under on-farm conditions using the sniffer method.

This study proposed a method for measuring the methane (CH 4 )/carbon dioxide (CO 2 ) ratio from individual beef cattle under on-farm conditions and estimated the variance components of the CH 4 /CO 2 ratio. Gas measurements were conducted using 166 Japanese Black cattle group-housed in pens equipped with individual feed bins. The gas containing the animal's breath was measured individually after concentrate feeding by covering the feed bin with a sheet with sampling inlets. Measurements were performed six times (three consecutive days, twice daily) per individual. Most of the sampled gas contained more than 1000 ppm of the mean background-corrected CO 2 , suggesting that the method proposed in this study successfully collected sufficient breath concentration to accurately measure the CH 4 /CO 2 ratio. The between-animal variance accounted for 31.7% of the total variance in the CH 4 /CO 2 ratio. The results showed that the gas collection method proposed in this study could be a useful tool for measuring the CH 4 /CO 2 ratio under on-farm conditions. The variance component obtained from this study will help to establish protocols for generating data for genetic evaluation and performing dietary experiments with sufficient statistical power.