Anticoccidial activity of Lasalocid in control of moderate and severe coccidiosis.

The fermentation product lasalocid ("Antibiotic X-537A," Hoffmann-LaRoche) showed good anticoccidial activity when administered via feed at 50 or 75 ppm in a replicated floor-pen experiment. Lasalocid was compared with monensin (121 ppm) ("positive control") and also with unmedicated ("negative") controls in pens heavily seeded or indirectly seeded with eight species of coccidia (Eimeria acervulina, E. brunetti, E. hagani, E. maxima, E. mitati, E. necatrix, E. praecox, and E. tenella). Under severe coccidiosis exposure (litter seeded by infected birds) both anticoccidials permitted significantly increased weights, improved feed conversions, and reduced lesion scores. Shank depigmentation was numerically less in anticoccidial-treated birds than in unmedicated controls, though not significantly. Coccidiosis mortality (lesions or parasites demonstrated) was 10% in unmedicated controls. Lasaloic reduced this mortality significantly to 0.8% at 50 ppm and 0.4% at 75 ppm. No coccidiosis mortality occurred with monensin-fed birds. With moderate exposure (indirect seeding) both anticoccidials permitted significantly greater weight gains and less shank depigmentation than in unmedicated controls. In unmedicated pens severity of coccidiosis was significantly greater in the intentionally seeded pens than in indirectly seeded pens with all parameters except depigmentation. This design provided a practical procedure for testing anticoccidials in a single experiment against severe and moderate exposures to coccidiosis as are normal in broiler production.