Effects of exogenous fibrolytic enzymes, alpha-bromoethanesulfonate and monensin on fermentation in a rumen simulation (RUSITEC) system

The effects of exogenous fibrolytic enzymes, alpha-bromoetbanesulfonate (BE S) and monensin on fermentation and digestibility of grass hay were examine d using two rumen simulation technique (RUSITEC) devices, each equipped wit h eight 820-mL fermenters with a liquid dilution rate of 0.73 d(-1). Grass hay (10 g d(-1)) was fed either untreated or pre-treated with 0.2 g each of cellulase and xylanase, and in combination with no chemical or daily dosin g of 20.5 mu mol monensin, 20.5 mu mol BES or 41 mu mol BES. Pretreatment o f hay with the fibrolytic enzymes increased (P < 0.05) organic matter (OM), cellulose and hemicellulose digestibilities by 9, 15, and 20%, respectivel y, and increased (P < 0.05) methane production per gram digestible OM by 43 %. With the enzyme treatment, both beta-endoglucanase and xylanase activiti es were enhanced (P < 0.05). Application of the enzymes promoted (P < 0.05) the growth of methanogenic bacteria, with no effect on total bacterial or cellulolytic bacterial populations. alpha-Bromoethanesulfonate did not infl uence digestibility, but depressed (P < 0.005) methane production by 51%. A ddition of BES inhibited (P < 0.05) growth of methanogenic bacteria, with n o effect On either the total or cellulolytic bacterial populations. Monensi n depressed (P < 0.05) OM, cellulose and hemicellulose digestibilities by 1 5, 27 and 17%, respectively, and methane production by 78%. Treating grass hay with fibrolytic enzymes enhanced fiber digestion but also methane produ ction. Including BES counteracted the methane production without affecting fiber digestion whereas monensin decreased both fiber digestion and methane production.