A note on the effects of monensin on the performance and on rumen metabolites of intact male cattle

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Abstract
Two groups of 14 intact male weanling beef breed calves were each fed 1·45 kg oat hay daily and concentrates ad libitum, in a 158-day feeding trial. Group ‘a’ received 35 p.p.m. monensin in the concentrate. Group ‘b’ served as a control.Average daily gain was 1·28 and 1·27 kg, dressing percentage was 58·1 and 58·0, daily intake of concentrate was 8·10 and 8·79 kg and conversion ratio of metabolizable energy into live weight was 74·53 and 81·30 MJ/kg for the monensin and the control group respectively. The percentage of acetic acid in rumen liquor was reduced and that of propionic acid increased very markedly. As a result the acetic acid: propionic acid ratio was reduced from 3·2 in the control group to 1·8 in the monensin group. No peculiarity in the response of intact male cattle to monensin was observed.