Pathology in Practice

摘要

In a flock of 27-day-old commercial broiler chickens in southeast Alabama, there was a noticeable increase in mortality rate in 1 of the 4 houses in which the birds resided. The field technician responsible for this flock reported that several birds in the affected house were small and listless and had ruffled feathers; some birds were recumbent and un- able to rise. Of 37,300 birds originally placed in the affected house at 1 day after hatching, 194 had been found dead over a 3-day period (61, 76, and 57 deaths among the 24-, 25-, and 26-day-old birds, respectively). The expected mortality rate at this age and in a flock of this size was < 15 birds/d. Prior to the placement of birds in the house, the used litter had been removed and the house was bedded with fresh peanut hulls. The birds in the flock had been hatched at a local hatchery that participated in the National Poultry Improvement Plan. The eggs from which the birds hatched had been produced by breeder stock that were monitored accordingto the guidelines of the National Poultry Improvement Plan; under that certification scheme, the stock wereclassified as Mycoplasma gallisqpticum monitored, Mycoplasma synoviae monitored, and avian influenza clean. The birds were vaccinated against Marek's disease virus in ovo at 18 days of incubation and spray vaccinated against Newcasde disease virus and the Arkansas strain of infectious bronchitis virus prior to leaving the hatchery. However, because of the recent increase in the number of deaths, 6 live birds from the affected house were submitted to the J. B. Taylor Veterinary Diagnostic Laboratory in Elba, Ala, for examination.