Evaluation of decoquinate or lasalocid against coccidiosis from natural exposure in neonatal dairy calves.

Forty-one Holstein and Brown Swiss calves were raised as herd replacements under conditions in which they were allowed natural exposure to sporulated coccidial oocysts at a very early age. Two compounds previously shown to have anticoccidial efficacies, decoquinate and lasalocid, were used for this study. Calves were assigned randomly at birth to one of the treatments: decoquinate (approximately .5 mg/kg of BW) or lasalocid (approximately 1.0 mg/kg of BW) or to remain as unmedicated controls through 16 or 24 wk of age. Counts of fecal oocysts were reduced in the calves fed decoquinate for wk 4 to 8 and for both treated groups for wk 9 to 24. Calves fed decoquinate had increased BW, heart girth, and height at withers during wk 5 to 8. Both treated groups had higher gains than untreated calves during wk 12 to 16 with the decoquinate group larger than the lasalocid group. Feeding an anticoccidial compound to newborn calves reduced severity of coccidiosis when early natural exposure occurred.