Are dietary strategies to mitigate enteric methane emission equally effective across dairy cattle, beef cattle, and sheep?

摘要

The digestive physiology of ruminants is sufficientlydifferent (e.g., with respect to mean retention time ofdigesta, digestibility of the feed offered, digestion, andfermentation characteristics) that caution is neededbefore extrapolating results from one type of ruminantto another. The objectives of the present study were (1)to provide an overview of some essential differences inrumen physiology between dairy cattle, beef cattle, andsheep that are related to methane (CH_4) emission; and(2) to evaluate whether dietary strategies to mitigateCH_4 emission with various modes of action are equallyeffective in dairy cattle, beef cattle, and sheep. A literaturesearch was performed using Web of Science andScopus, and 94 studies were selected from the literature.Per study, the effect size of the dietary strategieswas expressed as a proportion (%) of the control levelof CH_4 emission, as this enabled a comparison acrossruminant types. Evaluation of the literature indicatedthat the effectiveness of forage-related CH_4 mitigationstrategies, including feeding more highly digestiblegrass (herbage or silage) or replacing different foragetypes with corn silage, differs across ruminant types.These strategies are most effective for dairy cattle, areeffective for beef cattle to a certain extent, but seem tohave minor or no effects in sheep. In general, the effectivenessof other dietary mitigation strategies, includingincreased concentrate feeding and feed additives(e.g., nitrate), appeared to be similar for dairy cattle,beef cattle, and sheep. We concluded that if the modeof action of a dietary CH_4 mitigation strategy is relatedto ruminant-specific factors, such as feed intake or rumenphysiology, the effectiveness of the strategy differsacross ruminant types, whereas if the mode of actionis associated with methanogenesis-related fermentationpathways, the strategy is effective across ruminanttypes. Hence, caution is needed when translating effectivenessof dietary CH_4 mitigation strategies acrossdifferent ruminant types or production systems.