The Impact of Increasing Anthelmintic Resistance on Ruminant Performance and Greenhouse Gas Emissions

Abstract We are unlikely to see reductions in greenhouse gas (GHG) emissions from ruminants in the UK without changes to the way we farm. However, there are many ways in which emissions can be reduced, without reducing our meat and milk output (which raises the risk of displacement of production and emissions). Improving productivity often leads to reductions in emissions intensity (EI, the kg of GHG emitted per kg of output), thereby enabling emissions to be reduced while maintaining output. One way of improving productivity is to improve ruminant health. Helminth parasites (roundworms and fluke) are among the most important production-limiting pathogens of grazing livestock in the UK. However, there is also evidence of increasing anthelmintic resistance (AR) among some important parasites, which could render current treatments less effective. In this case study, we review the evidence on trends in ruminant emissions and explain why health status is an important determinant of GHG emissions. We then review trends in AR and outline options for tackling it. Information © The Authors 2025