In the United States, virtually all broiler chickens (those raised for meat) and turkeys come from strains produced by four and three primary breeding companies, respectively. Within several hours after hatching, the chicks are typically relocated from the hatchery or breeder farm to the commercial grow-out facility via ground and air transportation. Small hatcheries also send chicks to backyard “hobbyists” via U.S. Postal Service delivery.
Unlike adult birds and mammals, who are able to regulate body temperature metabolically, recently hatched chicks cannot fully self-regulate their body temperature. As a result, they are sensitive to heat stress and are especially prone to becoming chilled, thereby requiring an external heat source. Because of the special
temperature requirements of chicks during the first week of life, affording them protection from environmental extremes of heat and cold during transport is both critically important and challenging.
Since chicks have a limited store of nutrients at hatching, the duration of transport has a significant impact on the animals’ physiological condition. Shipments of newly hatched chicks may be comprised of both early- and late-hatching chicks, meaning the animals can vary in age by 21 to 36 hours. As a result, early-hatching chicks may be deprived of food and water for a longer period of time before transport.
Dead-on-arrival (DOA) mortality percentage of chicks transported by aircraft is proportional to travel time. For journeys approaching 72 hours, the mortality rate was more than 11%, while the seven-day mortality (including DOAs) for chicks was nearly 50%.
Arguably, high temperature is the most severe stressor that chicks face during transport. At high temperatures and high humidity, the ability to regulate body temperature through water evaporation by panting becomes difficult