Effect of Monensin on Beef Cattle Performance

Abstract

Growing-finishing beef steers fed 33 ppm monensin, starting at an initial weight of 270 kg and fed for 232 days gained at an identical rate (.89 kg per day) with cattle receiving no monensin, but required 10% less dry matter per kilogram gain (701 vs 778 kg). Rumen volatile fatty acid samples at 56 days on experiment showed a 16% decline in acetic acid (53.6 vs 64%); a 76% increase in propionic acid (38.7 vs 22%); and a 14% decline in butyric acid (7.8 vs 14%) due to the monensin treatment. At time of slaughter, cattle fed monensin graded one half grade lower and had a higher incidence of liver condemnation (56 vs 8%). Monensin had no effect on the growth-stimulating effect of diethylstilbestrol (DES), but the monensin effect on VFA production was significantly increased by DES.