Supplementing dairy cows with oils to improve performance and reduce methane – does it work?

Abstract

Oil supplements can be used in dairy rations to increase dietary energy density (and energy intake) and reduce methane (CH 4) emissions from rumen fermentation. Trials at Dexcel measured effects of oil supplementation on dry matter intake (DMI), milk yield and methane production after lactating dairy cows were fed pasture-based diets for short (14-day) and long (12-week) periods. In the short-term trial, 32 cows received either no oil or three mixtures of sunflower and fish oil at 500g/d. In the long-term trial 20 cows grazed pasture and received either no oil or 300g linseed and fish oil for 11 weeks prior to methane measurements. The type of oil in the short-term trial did not affect methane production and oils had no effect on DMI or milk yield but reduced total methane emissions by 27% (176 vs. 242g CH 4 /cow/d, sed=10.6) and CH 4 /kg DM (13.5 vs. 18.5g CH 4 /kg DM, sed=0.88). In the long-term trial, oil had no effect on methane emissions (353 (oil) vs. 323g CH 4 /cow/d (control), sed=17.0 and 21.7 vs. 23.0g CH 4 /kg DM, sed=1.01). These trials did not show benefits of oils for milk production and emphasize the need for long-term studies when developing on-farm strategies for methane mitigation.