Poultry are exposed to a number of concurrent stressors during transportation. It is proposed that thermal challenges (both elevated thermal loads and cold stress) constitute the main threat to the birds’ welfare and survival. The effects of thermal stress may be exacerbated by extended withdrawal of food or water and by exposure to vibrations and accelerations. Existing pathologies and injuries may further compound the situation.
Whilst genetic selection in broiler chickens has resulted in major improvements in growth rates and production efficiency these advances may also be associated with a reduced resistance to thermal stress, altered heat exchange capacity and muscle and cardiovascular pathologies. These path-physiological states may render the birds more susceptible to thermal stress and may form a part of the “transport stress” experienced by poultry and lead to increased mortalities during exposure to hostile thermal microenvironments in transit and contribute to the observed increase in transport mortalities seen during challenging meteorological conditions.
Welfare during transport may be improved by a more holistic consideration of the birds’ physiology, rearing conditions, pre-transport handling and the prevailing conditions and stressors that may be imposed during the journey.