Monensin feeding trial with young growing bulls

The effect of monensin ongrowth and feed utilization was studied in male calves of milk breeds, mainly Ayrshire. After weaning they were kept in an indicated loose-housing type shed divided into four strawbedded pens. The experiment was started at the age of 2—3 months and lasted 16 weeks. A concentrate mixture and grass silage were offered ad libitum. The concentrate given to the test groups had a monensin content of 35 ppm. Monensin lowered the feed consumption: in the control and test groups the intake of concentrate was 3.9 and 3.7 kg DM, respectively, the silage intake was 0.8 and 0.7kg DM, the fattening feed unit intake was 4.65 and 4.36, and the ME 54.4 and 50.9 MJ per day. The liveweight gain was not affected (1328 and 1329 g/d). Monensin improved the feed conversion rate by 6 %. The animals in the test groups were slightly cleaner than the animals in the control groups