Broiler transportation in Saskatchewan
Knezacek, Tennille D.
The thermal micro-environment of trailers transporting broiler chickens in Saskatchewan was investigated by recording temperature and relative humidity (RH) with data loggers. Initially, four cold weather journeys, where the ambient temperature ranged from -28.2 to -7.1°C, were conducted and conditions at the core of the trailer were monitored. Temperature variations were evident throughout the trailer and results demonstrated the potential for cold stress near air inlets and heat stress in areas with poor air circulation, particularly around the step in the trailer frame. The physiological effects of transportation on the birds were measured by taking rectal temperatures immediately before and after transportation and by introducing birds that had been previously implanted with devices for recording deep body temperature to selected modules. Body temperature recordings indicated the probability of hyperthermia and hypothermia developing while birds were transported. Mortality associated with the cold weather journeys was high and ranged from 0.7 to 1.4%. The need to distinguish between birds dying in transit (DOA) and birds dying in lairage, while awaiting slaughter (DOS), was revealed. Horizontal and vertical temperature and RH gradients were examined in 27 additional journeys where the ambient temperature ranged from -27.2 to 21.9°C. The RH sensors did not function in cold weather, but when the ambient temperature was above O°C, ambient RH ranged between 30 and 89%. Mean temperature lift, or the difference between ambient and on-board temperature recordings, was more pronounced during cold weather journeys with the curtains lowered compared to warm weather transportation with the curtains retracted. With both curtains lowered, open vent area affected mean temperature lift. With both curtains raised, the maximum temperature lift with the headboard and tailboard vents open was 2.5°C lower than with the front and rear vents closed. Apparent equivalent temperature (AET), indicating the effective temperature for broilers in transit, suggested that as ambient temperature dropped below O°C, more birds were exposed to potentially dangerous AET due to cold air entry on the trailer. At the same time, dangerous AET indicative of heat stress developed in the core of the trailer. As ambient temperature approached 16°C, AET values reflected safe conditions for transported broilers; however, as the ambient temperature surpassed 16°C, the potential for bird stress increased. Moisture on the trailer, primarily from bird respiration, contributed significantly to the AET experienced by the broilers. Mean DOA and DOS mortality was 0.14 and 0.28%, respectively, and dead birds were found distributed throughout the trailers. DOA losses were not affected by journey length, but both DOA and DOS mortality were affected by ambient temperature and stocking density. Ambient temperature below -16°C and a stocking density of 26 birds per crate significantly increased DOA and DOS values. However, high mortality losses associated with one cold weather journey, which was the only journey conducted at a stocking rate of 26 birds per crate, may have skewed the results. Despite higher than recommended levels at some facilities, atmospheric ammonia did not affect bird mortality. Although on-farm management can predispose birds to transportation stressors, the barns participating in this study were well managed and contained birds in good condition.