Effect of Monensin on Gains of Steers Grazed on Coastal Bermudagrass

Abstract

A 140-day grazing trial was conducted to determine the effects of various levels of monensin on gains made by steer calves and yearlings while grazing Coastal bermudagrass pasture. Cattle on all treatments were grazed on Coastal bermudagrass forage at a stocking rate of 2.5 head per acre (6.2 steers per hectare). Corn, yellow, grnd., pelleted, 4 02 992 (ground, pelleted corn) was fed at a rate of 2 lb (908g) per head daily as a carrier for the appropriate monensin levels. The treatments were no corn, corn only, and corn plus 25, 50, 100, or 200 mg monensin per head daily. Each treatment was replicated twice. Ten cattle, with equal numbers of steer calves and yearling steers, were grazed in each replicate. The cattle were rotated among pastures within each set of replicates at 7-day intervals. Cattle on all levels of monensin produced larger (P<.05) weight gains than the control cattle. Animals fed corn with no monensin performed better than those on forage only. Growth rates of the steers receiving monensin increased as the drug level increased through 100 mg per head daily. Cattle fed the 200 mg level of monensin gained only slightly, but significantly, more than those on the 25 mg level.