Coccidial infections acquired by sentinel birds exposed to litter from experimental and commercial broiler chickens1

A method devised to monitor the potential coccidial challenge present in commercial broiler house litter appears to have practical value. Coccidial infections were acquired by coccidia-free chickens (sentinel birds) exposed to infected litter for a brief (48-hour) period. Coccidial lesion scores and body weight changes in sentinel birds after exposure to litter were used to estimate coccidial infections. The inclusion of medicated groups of sentinel birds enabled an evaluation to be made of the efficacy of anticoccidial drugs on naturally acquired coccidial infections arising from exposure to commercial broiler house litter. The coccidial challenge of reused commercial broiler house litter was compared with litter new at the start of the crop. Only slightly higher coccidial challenge resulted from the reuse of litter. Oocyst counts were relatively high in litter from experimental pens and there was some correlation between numbers of oocysts found in the litter and infection acquired by sentinel birds. Conversely, the coccidial infections acquired by sentinel birds exposed to commercial broiler house litter did not correlate with the number of oocysts found in the litter to which they had been exposed. This indicates that litter oocyst counts are a relatively insensitive method for predicting potential coccidial challenges in broiler chickens.