Performance, feed efficiency, methane emission and rumen microbiome in lactating dairy cows fed a grass-clover silage-based diet supplemented with an essential oil blend

Emission of enteric methane from cattle is a challenge for sustainable milk production. Blends of essential oils (EO), as a feed additive, have the potential to reduce enteric methane from cattle. The aim of the present study was to evaluate dairy cow performance, methane emissions and rumen microbiome, when fed a grass-clover silage-based diet supplemented with a blend of EO from the company Agolin SA (AR). Thirty-six Holstein cows were allocated to one of two treatment groups and were fed either a standard TMR diet, or the same diet added 1 g per cow per day of the AR product, which contained 200 mg active blend of EO. The experiment was conducted for a period of 10 weeks in a continuous design plus a pre-period of 1 week. The cows had free access to GreenFeed methane measurement devices throughout the experiment. Individual dry matter intake (DMI), milk yield, milk composition, rumen volatile fatty acids (VFA) were measured. Rumen microbiome was analyzed from metagenomic sequencing of DNA from rumen samples and quantitative PCR targeting total Bacteria, Archaea, Fungi and Protozoa. There was no effect of AR on DMI ( P = 0.25), energy-corrected (ECM), milk yield ( P = 0.47), or feed efficiency ( P = 0.64). Furthermore, there was no significant effect of AR on production of methane per day ( P = 0.67), per kg DMI ( P = 1.00), or per kg ECM ( P = 0.71). In conclusion, adding 200 mg of EO to diets with a high proportion of grass-clover silage had no significant effect on dairy cow performance, methane emissions, rumen fermentation or rumen microbiome. • Rumen modifiers are needed to reduce enteric methane production. • A blend of essential oil from Agolin SA (AR) was fed to dairy cows. • Cows were fed a high grass-clover silage based diets (54.4 of dietary DM%). • Dry matter intake, milk yield and composition and feed efficiency were not affected by AR. • Methane production (g/d), and methane per kg of dry matter intake were not affected by AR.