Compositional and structural dynamics of the ruminal microbiota in dairy heifers and its relationship to methane...

Heifers emit more enteric methane (CH₄ ) than adult cows and these emissions tend to decrease per unit feed intake as they age. However, common mitigation strategies like expensive high-quality feeds are not economically feasible for these pre-production animals. Given its direct role in CH₄ production, altering the rumen microbiota is another potential avenue for reducing CH₄ production by ruminants. However, to identify effective microbial targets, a better understanding of the rumen microbiota and its relationship to CH₄ production across heifer development is needed.

Here, we investigate the relationship between rumen bacterial, archaeal, and fungal communities as well as CH₄ emissions and a number of production traits in prepubertal (PP), pubertal (PB), and pregnant heifers (PG). Overall, PG heifers emitted the most CH₄ , followed by PB and PP heifers. The bacterial genus Acetobacter and the archaeal genus Methanobrevibacter were positively associated, while Eubacterium and Methanosphaera were negatively associated with raw CH₄ production by heifers. When corrected for dietary intake, both Eubacterium and Methanosphaera remained negatively associated with CH₄ production.

We suggest that Eubacterium and Methanosphaera represent likely targets for CH₄ mitigation efforts in heifers as they were negatively associated with CH₄ production and not significantly associated with production traits. © 2018 Society of Chemical Industry.