Animal Nutrition and Feed Technology

Bromoethanesulfonic acid (BES) was examined as a methane inhibitor and its impact on rumen microbial populations in male cattle calves. Ten crossbred cattle calves (average body weight, 132±2 kg) were divided into two groups of five each and were fed on a diet containing 19.9% CP and 72.6% TDN. In the experimental group, BES was fed at the rate of 5 mg for first 10 days, 10 mg for next 10 days (11–20^th day) and 15 mg/kg BW for another 10 days (21 to 30^th days) of the experiment. Rumen liquor was collected by stomach tube from calves after feeding of each level of BES and was used for studying the microbial profile by real time PCR and as an inoculum for in vitro gas production test. The in vitro methane production (ml/g DDM) was reduced (P<0.05) by 35, 8.1 and 15 per cent on feeding BES at the levels of 5, 10 and 15 mg/kg BW (P<0.001, P=0.007 and P=0.009, respectively). The in vitro true digestibility of feed was not affected at lower levels but was significantly improved at 15 mg BES level (P=0.026). The population of protozoa, was significantly reduced at 5 mg BES (P=0.014) level but at 10 mg level, fungi and methanogens were reduced significantly (P=0.031, P=0.034) and at 15 mg BES level only fungal population was reduced (P=0.029). The results indicated that BES can reduce rumen methanogenesis but cannot eliminate methanogens completely from the rumen.