Dietary strategies aiming to reduce the environmental impact of ruminants

Ruminant livestock are responsible for non-CO2 greenhouse gas (GHG) emissions, namely methane from enteric fermentation and nitrous oxide, as indirect emissions from manure management. Reduction measures of GHG must be taken by all sectors to reach the European greenhouse gas production targets of 55% of net reduction by 2030 and of neutrality by 2050 (European green deal, Paris agreement). It has to be highlighted that livestock partly exploit resources, which are not in competition with humans, and enteric methane is a physiological need of ruminants; therefore, its production can be reduced but not eliminated. Despite this evidence, in the last decades, several feeding strategies have been proposed, which overall are pointing toward the improvement of animal efficiency and the reduction of their methane emission. Among these approaches, good practices in grazing management, forage harvesting and preservation strategies, together with the inclusion of concentrate of dietary fats, might help in mitigating the environmental impact of ruminants. Furthermore, several in vitro studies have reported the potential of including various feed additive types, either as pure or as a mixture, but confirmations in vivo are required.