Lasalocid: resistance and cross-resistance studies in Eimeria tenella-infected chicks

Eimeria tenella was passaged in the presence of suboptimal and optimal concentrations of lasalocid (X-537A, sodium salt) in feed. Lasalocid was equally active at concentrations of 0.006 and 0.0075% against the 10th and 15th passage of E. tenella lasalocid exposed strains. Resistance to lasalocid could not be induced. Lasalocid administered in the feed at 0.0075% was tested in controlled battery experiments against E. tenella strains resistant to known anticoccidials in chicks. These studies demonstrated that lasalocis, at the optimal feed concentration of 0.0075% was highly effective against coccidiosis induced by strains of E. tenella resistant to sulfaquinoxaline, nicarbazine, zoalene, emprolium, clopidol and 4-hydroxyquinoline. Lasalocid medicated chicks were heavier, converted feed more efficiently, showed less pathologic lesions, and had lower mortality (P less than or equal to .05) than the infected unmedicated controls as well as sulfaquinoxaline, nicarbazine, zoalene, amprolium-ethopabate, clopidol, buquinolate, decoquinate and nequinate medicated groups. Cross-resistance to lasalocid was not demonstrated.

Influence of rofenaid-40 feed medication on an experimental Salmonella infection in chickens

Rofenaid-40 administered at 0.02% in feed to chickens experimentally infected with Salmonella typhimurium resulted in less colonization and shedding of S. typhimurium than in unmedicated chickens. The antibacterial sensitivity pattern of S. typhimurium isolated from infected birds had not changed after exposure to Rofenaid for 56 days.