Abstract
The effect of monensin on the production of gases and of VFA in the rumen was investigated under the conditions of the switch back trial using Czerkawski's small scale apparatus, which was composed of two 50ml syringes connected by a three way tap. A sample of rumen contents was taken from four fisturated wethers which had received a high roughage ration with or without 20ppm monensin, an hour before and seven hours after the morning feeding. The amounts of gases and VFA produced during incubation at 39°C for four hours were calculated by subtracting the amount of gas originally dissolved in the inoculum before incubation from that found after incubation. Production of total gas, carbon dioxide and methane significantly decreased by the supplementation of monensin. Acetate production decreased, but propionate increased and butylate was not affected. These effects of monensin lasted during the experimental period of 21 days of monensin supplementation, but the effects was disappeared seven days after the withdrawal of monensin.
