Evaluation of an enrofloxacin-treatment program against Mycoplasma gallisepticum infection in broilers.

Three chicken broiler breeder flocks, 7 months of age, were confirmed to have Mycoplasma gallisepticum (MG) infection, based on culture of tracheal swabs. A total of fifty-five 7-day-old embryos from the three MG-positive flocks had an average 27.4% prevalence of MG-infection in their vitelline membrane. Sixty randomly selected MG isolates (30 from individual tracheas of breeders and another 30 from individual vitelline membrane of embryos) were highly sensitive in vitro to enrofloxacin (100%). Three broiler flocks (averaging 15,000 birds per flock) from the same three MG-infected chicken boiler breeders were divided into halves. The first halves were subjected to an enrofloxacin-treatment program and the other halves were controls. Sera collected at different ages of the broiler flocks were tested by the enzyme-linked immunosorbent assay for antibodies to MG. The absence of MG titers at 45 days of age in birds subjected to the enrofloxacin-preventive program was compared to an average prevalence of 15.9% in the controls (p < 0.05). The lack of MG titers in 45-day-old birds subjected to the enrofloxacin-treatment program was associated with lower better feed-conversion ratios (p < 0.05).