Current situation and problems of built-up litter system for rearing management in a broiler farm

A broiler farm in Kumamoto Prefecture with decreased performance was subjected to diagnostic inspection in May 2008. Houses for floor feeding were subsequently managed under the built-up litter system. Three dead chickens from each broiler house were examined at weekly intervals to diagnose diseases. The inspection results suggested that the increased mortality of 22- and 29-day-old chickens was primarily due to colibaccilosis, and that of 36-day-old chickens was primarily due to coccidiosis. The ammonia gas concentration in the broiler house was very high, and coccidial oocysts were detected in the built-up litter just after treatment for reuse. Mortality decreased after depopulation of chickens and improvement of the built-up litter system and environmental conditions of chicken houses. In contrast, no improvement of performance was obtained before isolation of Escherichia coli from the chickens, even though the managing veterinarian had prescribed enrofloxacin for the farm. The E. coli isolates were not sensitive to enrofloxacin. Progressive resistance to enrofloxacin among E. coli isolates from five broiler farms where outbreaks of colibacillosis had been detected was also confirmed. These results suggest that enrofloxacin-resistant E. coli might be increasing.