Indirect Estimation of CH(4) from Livestock Feeds through TOCs Evaluation

Thirty-five available feeds were fermented in vitro in order to investigate their soluble total organic carbon (TOCs) and methane (CH(4)) production rate. A fermentation reactor was designed to capture the CH(4) gas emitted and to collect liquor from the reactor during in vitro fermentation. The results showed that CH(4) production rate greatly varied among feeds with different ingredients. The lowest CH(4)-producing feeds were corn gluten feed, brewer’s grain, and orchard grass among the energy, protein, and forage feed groups, respectively. Significant differences (p<0.05) were found in digestibility, soluble total organic carbon (TOCs), and CH(4) emissions among feeds, during 48 h of in vitro fermentation. Digestibility and TOCs was not found to be related due to different fermentation pattern of each but TOCs production was directly proportional to CH(4) production (y = 0.0076x, r(2) = 0.83). From this in vitro study, TOCs production could be used as an indirect index for estimation of CH(4) emission from feed ingredients.