Production, Management and the Environment: General

In addition to having methods for depopulation of commercial poultry flocks to contain outbreaks of serious avian disease, there is need to have an efficient and humane method to dispose of small flocks that might fall within an affected area. A modified atmosphere killing (MAK) chamber mounted on a trailer to be pulled by a pickup truck was designed for small flock depopulation. The atmosphere inside the chamber is controlled automatically using gas sensors. A portable gasoline generator drives the electronic systems so no external electrical supply is required. The chamber (152.5 cm W × 152.5 cm L) has a total interior volume of about 2.1 m3, with a 1 m3 section to hold birds below gas injection nozzles distributed 44.5 cm above the floor around the perimeter of the chamber. The chamber rises to a height of 51 cm to provide sufficient head space to load birds through 4 doors, 2 on each side of the chamber. The loading doors can be sealed shut and the trailer sanitized by a disinfectant solution pumped from a self-contained 114 L tank before the trailer leaves the premises to deliver a killed flock to a disposal site. A hydraulic lift facilitates dumping of carcasses. The MAK trailer was tested in several trials using spent layer breeder hens, spent laying hens, and turkey hen broilers. CO2 levels during loading were targeted at 45–50%. The highest rate of loading was 2.8–3.4 s per bird during trials with the spent layer breeders. Since the floor capacity of the chamber is about 100 birds, this rate of loading is unlikely to cause birds to be overlain by others before onset of unconsciousness. Chamber temperature and RH during turkey trials ranged from 24 to 29 C and RH from 55 to 85%. Maximum loads ranged from 305 to 440 hens (total wt. 567–609 kg), and 79 turkeys, (555–560 kg). In its final configuration, the MAK unit was able to maintain effective stunning/ killing atmospheres during use. Loading could be continuous when CO2 was used but N2 required birds to be killed a layer at a time to prevent piling of conscious birds.