Abstract
The preventive effect of sulfamonomethoxine (Smm) and ormetoprim (Omp) medicated in combination against leucocytozoon infection in chickens was tested in field trials. In trial 1, medication was given continuously throughout the experimental period. In trial 2, medication was given for seven days and no medication was given for the next seven days; then this schedule for the medication was repeated throughout the experimental period. In trial 1, almost complete prevention was obtained when Smm and Omp were added to the feed at the level of l2 ppm and l4 ppm, respectively, or at the level of 15 ppm and 5 ppm, respectively. Only a partial effect was obtained, however, when these drugs were used at the level of 9 ppm and 3 ppm, respectively. In trial 2, a nearly complete effect was obtained when Smm and Omp were added to the feed at the level of 18 ppm and 6 ppm respectively, but we found no effect when these drugs were used at the level of 15 ppm and 5 ppm, respectively. There were no significant differences among the groups as to the weight gain.
