Repeatability of enteric methane measurements using GreenFeed systems on upland pastures

Session 34. Nutrition management to reduce methane emission and environmental impact

International audience

anglais. Plant diversity of mountain pasture has been shown to reduce enteric methane (CH4) production in vitro. In 2023,we set up an in vivo experiment to measure enteric CH4 emission using GreenFeed (GF) systems and dairy performancesof 28 grazing dairy cows on mountain pasture. After 3 weeks of being fed fresh grass indoor, they weretaken out to extensively managed pasture for 9 weeks. Cows were allowed to graze large areas (from 1 to 3.5 ha),and 2 GF equipped with solar panels were accessible near the water trough. As lower frequency of animal visitsto the GF at pasture than indoor was expected, our aim was to determine the minimum number of consecutiveCH4 spot measurements (CSM) to achieve a good repeatability of CH4 data. As expected, the average number ofvisits per animal and per day (d) was 2.6 ± 0.42 vs 0.7 ± 0.24 during indoor vs grazing periods. Five to 20 CSMwere randomly chosen within the set of available data per animal per period (indoor vs outdoor) and the drawswere repeated 10 times. The analysis was repeated 5 times to evaluate the consistency of the results across draws.Results showed that a minimum of 15 CSM acquired in 12 and 29 d was necessary to achieve a similar repeatabilityof 0.53 and 0.50 indoor vs at pasture, respectively, with a low variability across repetitions and no effect ofthe interval between first and last CSM. If performances of GF measurement indoor or in small plots of intensivepasture are documented, it is the first time at our knowledge that their performances were studied under extensivegrazing conditions on natural grasslands in Europe.