Anticoccidial Activity of Lasalocid (X-537A) in Chicks

Lasalocid (X-537A, Ro 2-2985 sodium salt), at graded feed concentrations, was tested in controlled battery experiments against various strains of single and mixed Eimeria species infections. The experimental data indicated that lasalocid, at dosages of 0.01, 0.0075 and 0.005%, demonstrated a high degree of anticoccidial activity in terms of preventing or reducing mortality, suppressing lesion scores, allowing for normal or close-to-normal weight gain and feed conversion against all major pathogenic species, E. tenella (11 strains), E. necatrix (4 strains), E. acervulina (4 strains), E. maxima (3 strains), E. brunetti (2 strains), E. mivati (2 strains) and E. praecox, single and mixed infections of the above-mentioned species. Lasalocid, at dosages of 0.01, 0.0075 and 0.005% in feed, exhibited a high degree of activity against 12 Eimeria field isolates coming from different geographic areas of the country and previously fed various commercially available coccidiostats. In floor pen trials, lasalocid, fed over an 8-week period to broiler chicks experimentally infected with 6 species of Eimeria, exhibited a high degree of efficacy at dosages of 0.0075 and 0.005% in feed. The statistical analysis of data demonstrated that lasalocid-medicated, infected chicks at cited dosages were heavier (P < .005 –.05), converted feed more efficiently (P < .005 –.05), showed a lesser degree of pathology (P < .005 –.05) and that mortality was prevented or reduced (P < .005 –.05), when compared with the infected unmedicated controls. These studies, involving 46 trials totaling 11,880 broiler chicks, have demonstrated that lasalocid, at the optimal level of 0.0075% in feed, is suggested as an aid in the control of avian coccidiosis in broiler flocks. This projected use level (0.0075%) is effective, palatable and safe.