Effect of monensin on the performance of grazing Boran Zebu bulls and Ogaden sheep during the dry season in Ethiopia.

Two short-term experiments were carried out with the polyether antibiotic monensin in East Ethiopia during the dry season. Monensin was given to 10 Boran Zebu bulls (84 days) and 15 female Ogaden sheep (112 days). All animals were grazing all day long on very poor rangeland. In the barn during the night, the animals were fed low concentrates, supplemented with 100 mg monensin per animal and day for bulls and 15 mg for sheep. The animals of the control croup did not receive any supplements. Monensin addition increased the daily weight gain of bulls from 15 to 89 g/animal (alpha greater than 0.05) and decreased the weight losses of the Ogaden sheep from 22 to 12 g/animal per day. The feed intake of grazing animals was not registered. Further experiments are recommended including more animals and longer experimental periods with antibiotics influencing the rumen fermentation to be carried out under tropical rangeland conditions.