Effect of various levels ofmonensin on efficiency and production of beef cows

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Journal of Animal Science




American Society of Animal Science

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Ninety-six gravid cows were allotted to three replications of four treatments. Monensin treatments consisted of 0, 50, 200 and 300 mg per head per day. The basic feed was meadow hay with .45 kg of barley per head per day. Feed was adjusted periodically to maintain equal weight gain between treatments. Initial cow weights for the control, 50-, 200- and 300-mg treatments were 45 5, 447, 456 and 457 kg, respectively. Daily prepartum cow gains were .34, .38, .38 and .37 kg (P>.05) for the control, 50-, 200-and 300-mg levels, respectively. Treatments were terminated about 30 days after calving. Over the entire treatment period, including 30 days postpartum, daily losses for the cows were .12, .05, .10 and .17 kg (P>.05) for the control, 50-, 200- and 300-mg levels, respectively. Hay consumption was 92, 88 and 90% of the controls for the 50-, 200- and 300-mg groups. Adjusted weaning weights for the calves were 124, 134, 129 and 133 (P>.05) for the control, 50-, 200- and 300- mg groups, respectively, with calves being weaned at 139 days of age. Control cows came into estrus an average of 44 days postpartum as compared to 44, 41 and 45 days for the cows given 50-, 200-and 300-mg treatments, with no difference in conception rates. Concentration of rumen acetic and butyric acid production was reduced and propionic increased with the 200- and 300-mg levels. Monensin feeding improved efficiency and reduced hay requirements without reducing production or reproductive performance.


J. Anim. Sci. 50:385-390