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

Abstract

The effects of exogenous fibrolytic enzymes, α-bromoethanesulfonate (BES) and monensin on fermentation and digestibility of grass hay were examined using two rumen simulation technique (RUSITEC) devices, each equipped with 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 dosing of 20.5 µmol monensin, 20.5 µmol BES or 41 µmol BES. Pretreatment of hay with the fibrolytic enzymes increased (P < 0.05) organic matter (OM), cellulose and hemicellulose digestibilities by 9, 15, and 20%, respectively, and increased (P < 0.05) methane production per gram digestible OM by 43%. With the enzyme treatment, both β-endoglucanase and xylanase activities 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. α-Bromoethanesulfonate did not influence digestibility, but depressed (P < 0.005) methane production by 51%. Addition of BES inhibited (P < 0.05) growth of methanogenic bacteria, with no effect on either the total or cellulolytic bacterial populations. Monensin depressed (P < 0.05) OM, cellulose and hemicellulose digestibilities by 15, 27 and 17%, respectively, and methane production by 78%. Treating grass hay with fibrolytic enzymes enhanced fiber digestion but also methane production. Including BES counteracted the methane production without affecting fiber digestion whereas monensin decreased both fiber digestion and methane production. Key words: Fibrolytic enzymes, α-bromoethanesulfonate, monensin, digestibility, methane, RUSITEC