Effects of lasalocid and monensin in combination with roxarsone on lesion reduction and oocyst suppression in chicks infected with Eimeria tenella field isolates.

The anticoccidial activity of lasalocid, monensin, and roxarsone, alone and in combination, was evaluated against eleven Eimeria tenella recent field isolates. Lasalocid was used at 0.0075. 0.01, and 0.0125% activity drug in feed; monensin at 0.0099 and 0.0121%; and roxarsone at 0.005%. Further studies with lasalocid 0.0075%, monensin 0.0099% and roxarsone 0.005 and 0.0025% combinations were carried out against three E. tenella field isolates selected from the aforementioned strains. Lasalocid and monensin each exhibited a high degree of anticoccidial activity at all concentrations tested. Lasalocid and monensin fed in combination with roxarsone showed, in addition to high anticoccidial activity a further reduction in gross lesions and oocysts production, more pronounced at 0.005% level of roxarsone than at 0.0025%, compared to either medication alone or the roxarsone combinations. These positive effects were noted with all strains tested. The practical aspects of these findings are discussed.