Early life treatment with Lacticaseibacillus rhamnosus strains drives reduced enteric methane emissions in dairy heifers

BACKGROUND: Methane emissions from enteric fermentation in ruminant livestock make up 27% of anthropogenic methane emissions. RESULTS: Screening > 1,700 lactic acid bacteria identified Lacticaseibacillus rhamnosus FNZ118 (Kowbucha™ FNZ118) and L. rhamnosus FNZ142, (Kowbucha™ FNZ142) as capable of inhibiting rumen methanogens and methane production in vitro. FNZ118 or FNZ142 fed daily to Friesian heifer calves from birth to 14 weeks substantially lowered methane production through the first year of life compared to control animals. These strains also decreased feed intake and reduced ruminal metabolite concentrations without affecting animal live weight, suggesting an improvement in feed conversion efficiency. The observed effects did not cause major changes in the structure of the rumen microbiome. CONCLUSIONS: production and have potential for the mitigation of enteric greenhouse gas emissions from growing dairy cattle.