EFFECT OF MONENSIN ON PERFORMANCE AND PLASMA METABOLITES IN GROWING-FINISHING STEERS

The effects of level of monensin on performance, feed utilization, carcass characteristics, plasma free amino acids and urea-nitrogen were studied with 96 yearling steers in a growing-finishing trial. Diets were composed of corn silage, ground shelled corn and soybean meal with monensin added to give the following treatments: (A) control, (B) 100 mg, (C) 200 mg and (D) increasing levels of 150 mg, 200 mg, 250 mg and then 300 mg monensin/head/ day. Feed intake on a dry-matter basis for the four treatment groups (A through D, respectively) were: 8.21; 8.07; 7.85 and 7.79 kg per day. Feed intake on all monensin treatments was lower (P.10). Differences observed for all metabolites with time on feed were significant (P<01). PUN increased with time on feed while GLU decreased. PAA increased during the early periods, then decreased with time on feed.