This study examined the effects of combining four feed additives; pyromellitic diimide (PD), rhubarb extract (RE), monensin (MO), and fumaric acid (FA), on performance and enteric methane emissions in sheep fed pelleted alfalfa diet. Inhibition of methane production in ruminants can increase the accumulation of hydrogen in the rumen. We hypothesized that when methanogenic inhibitors reduced methane, the accumulated rumen hydrogen could be utilized by hydrogen acceptors. The dietary additives did not affect intake or body weight gain; however, the inclusion of PD in the sheep diet at a dose rate of 50 mg/kg of dietary dry matter reduced methane emissions by ∼79% and increased the accumulation of rumen dissolved H₂ by 8-fold, compared with the Control or other additives. There was no effect of RE, MO, or FA on methane emissions. Accumulated hydrogen from methane inhibition appeared to be redirected to butyrate synthesis when RE was mixed with PD. However, FA failed to utilize rumen hydrogen while methanogenesis was inhibited. Interestingly, a full combination of four additives redirected the hydrogen in the rumen, by increasing the molar proportion of propionate and reducing the proportions of acetate, butyrate, and the acetate-to-propionate ratio.

Read the full article in the Journal of Animal Science.