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.