Propionate precursors and other metabolic intermediates as possible alternative electron acceptors to methanogenesis in ruminal fermentationin vitro

Abstract

Fifteen potential precursors of propionate were tested for their ability to decrease CH4production by ruminal fluidin vitro.Sodium acrylate and sodium fumarate produced the most consistent effects in batch cultures, with 50 % of the added precursors being fermented to propionate and CH4production decreasing by between 8 and 17 %, respectively. Additives were more effective when added as free acids, but this also decreased the pH and may have inhibited fibre digestion. Changing the dietary substrate from predominantly grass hay to predominantly concentrate had no influence on the effectiveness of acrylate and fumarate. In anin vitrofermentor (the rumen simulating technique, Rusitec) with a grass hay—concentrate (50:50, w/w) diet as substrate, both compounds were again fermented to propionate (33 and 44 % conversion to propionate, respectively). However, fumarate appeared more effective as a H2sink compound. It was calculated to capture 44 % of the H2previously used for CH4formation compared with a 22 % capture of H2with acrylate. Fumarate also caused a stimulation in fibre digestion. Thus, sodium fumarate was the preferred propionate precursor for use as a feed ingredient to decrease CH4emissions from ruminants.