Introduction
Day-old chicks' "welfare and growth, development and performance may be markedly influenced by the first episode of transportation between hatchery and rearing site."(1) As such, optimizing conditions is vital to reducing mortality rates during and following transport.
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.(2) 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.
Before hatching, chicks prepare themselves for their first few days of life by taking the yolk, a store of nutrients, into the abdominal cavity. The yolk "comprises approximately 20% of the body weight (BW) of chicks and provides immediate posthatch energy and protein for maintenance and growth."(3) However, commercial broiler chicks have been bred, in part, for unnaturally high metabolic rates, so the yolk may be nutritionally insufficient for these purposes.(4),(5) Absorption of the yolk should enable chicks to survive at least a short time without outside nutrients, but they are typically transported without food or water, which compounds the pressures on their bodies.
In a review of the scientific literature to date, it is suggested that "to simultaneously optimize survival, productivity and welfare of the newly hatched chick in transit, an effective strategy would be to match the thermal characteristics of the micro-environment to the biological requirements of the birds."(6) However, this recommendation is difficult, given the range of weather conditions found throughout the United States, where extremes can range from below 0°F to above 100°F, and temperature fluctuations of tens of degrees across geographical areas at the same time or at one place over just a few hours are common.
Air transport contributes additional challenges that can adversely affect chick welfare before, during, and following flights. As extremely low temperatures and atmospheric pressures are found at the altitudes at which commercial planes fly, cargo holds should be pressurized, heated, and ventilated to provide appropriate environmental conditions for live animal transport.(7) The lack of environmental control during the holding stages preceding and following flights can be even more detrimental to the chicks' welfare than the flights themselves.(8)
Duration of Transport
Since chicks have a limited store of nutrients at hatching, the duration of transport has a significant impact on the animal's 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 24 to 36 hours.(9),(10) As a result, early-hatching chicks are deprived of food and water longer before transport.
Xin and Rieger(11) reported that the dead-on-arrival (DOA) mortality percentage of chicks transported by aircraft was proportional to travel time. For journeys approaching 72 hours, the mortality rate was over 11 percent, while the seven-day mortality for chicks was nearly 50 percent. This was with an average box temperature of 31-35°C (88-95°F) during ground transport and 26-34°C (79-93°F) during flight.
The European Food Safety Authority's Scientific Panel on Animal Health and Animal Welfare caution that under some conditions "the food reserves of domestic fowl chicks are used up by 48h. When temperatures are high, they are used up much earlier."(12) Newer breeds of commercial birds have a much higher metabolism than older breeds, so the chicks are less equipped to "withstand long periods of inanition than chicks of 20 years ago."(13) One study concludes that delaying feeding of fast-growing broiler chicks by 48 hours can retard development, "which may not be offset by regular diet and hatchery practices."(14) Danish researchers investigating the effects of post-hatch delayed feeding on broiler chicks' growth and immune function find that "food deprivation for 48h may be unfavorable to the growth, viability, and immune performance"(15) and conclude that "(f)orty-eight hours without food is therefore not recommended."(16) Another study indicated that "the maximum fasting period, which had no significant negative effect on final weight, was 24h after the chicks were removed from the hatchers."(17) Providing access to nutrients during transport may mitigate effects of delayed feeding.(18)
Temperature
The effects of the environment on the health and growth of day-old chicks have been studied extensively, with research progressing from looking only at temperature effects to including details such as relative humidity and ventilation. Typically during transport, commercial containers or boxes are stacked one on top of another in tiers, with several boxes per tier and 80 to 100 chicks per box. Measured temperatures inside the containers placed in the center of the stack, both vertically and horizontally, can be 8-14°C (14-25°F) warmer than the ambient temperature, while the temperature of the boxes placed on the outer perimeter of the stack are likely closer to the ambient temperature.(19)
A comfortable, or thermoneutral, temperature for day-old chicks is approximately 31°C (88°F). Thermoneutral temperatures are often given as a range, defined by minimal metabolic rates or minimal expended energy to create or dissipate heat .(20),(21) Based on differing measurements of thermoregulatory effort, scientists vary in their proposed thermoneutral temperature ranges for day-old chicks, from ranges as narrow as 30-32°C (86-90°F)(22) or 32-35°C (90-95°F)(23) to more encompassing ranges, such as 31-37°C (88-99°F).(24) Critical temperatures bind this thermoneutral zone, and outside of these limits, an animal must adjust his or her behavior to thermoregulate. Investigating the effects of extreme temperature ranges on chicks, it was found that the upper critical temperature for day-old chicks is approximately 36-37°C (97-99°F)(25) and the lower critical temperature approximately 30°C (86°F).(26)
Examples in the scientific literature demonstrate that extreme temperatures quickly become lethal for chicks. Though much better equipped to thermoregulate than a day-old chick, a seven-day-old chick will die in less than three hours at an ambient temperature of 10°C (50°F).(27) A poultry breeding representative has noted that at freezing temperatures (0°C or 32°F), chicks cannot survive for more than 15 to 20 minutes.(28) Measurements taken during air transport studies of chicks recorded box temperatures exceeding 37°C (99°F) for up to several hours.(29) If held at slightly higher temperatures, above 40°C (104°F), the chicks' water stores are exhausted in eight to ten hours.(30)
Xin studied the effects of cycling temperatures over 50 hours on the body weight and mortality of chicks in commercial containers where half of the chicks had access to nutrients and water. Over the duration of the experiment, there was no significant decrease in mortality between the two groups—those afforded access to nutrients and those deprived. However, the research did not continue to monitor for mortality after the 50-hour experiment, when further effects of temperature stress and nutrient deprivation may have become apparent. The chicks who were given access to in-transit feed maintained their body weight better than those without access to nutrients, and Xin concluded that increased metabolic heat production due to a supply of nutrients "will greatly enhance the chick's ability to cope with cold stress."(31) Other research has shown that birds deprived of food for 48 hours have increased mortality rates under conditions of heat stress.(32) More work is needed in this area, but the availability of food and water during transport seems to improve the welfare of the birds transported over longer times and at extremes of temperatures.
Three decades ago, the believed optimal temperature range for transporting chicks was 16-20°C (63-67°F).(33) The International Air Transportation Association's (IATA's) current acceptable ambient temperature range for shipping day-old chicks is 14-23°C (57-73°F),(34) a range below most other recommendations. Several scientific studies, a breeder company, and the European Food Safety Authority's Scientific Panel on Animal Health and Animal Welfare currently recommend a temperature range for chick transport of 24-26°C (75-79°F).(35),(36) In a review of the recent literature, Mitchell and Kettlewell report that the ideal temperature and relative humidity (RH) range is 24.5-25.0°C (76-77°F) and 63-70 percent RH for transported chicks held at typical stocking densities. This recommendation is based on several physiological indicators of chick comfort, including minimal change in body temperature, hydration state, and electrolyte balance,(37),(38) and takes into account the heat generated inside the transport container by the chicks themselves. At these temperatures the microenvironment within the transport crate will be closer to 31°C (88°F).
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. It is in this situation that appropriate ventilation is important, "but its achievement is often difficult because of the construction of the crates and their proximity to one another."(39)
Ventilation
As noted, when traveling at higher temperature, it is critical to keep chicks well-ventilated to better allow for effective thermoregulation. With restricted ventilation (as in an aircraft), when temperatures around the transport container are at or above 34°C (93°F), the temperature inside the crate increases rapidly to exceed 40°C (104°F). At this elevated temperature, the chicks begin panting, which increases the relative humidity inside the container and effectively reduces the amount of heat loss by evaporation—effects that can increase body temperatures up to 43°C (109°F), inducing coma and death in chicks within 40 to 50 minutes.(40)
Midwest Plan Service, a university-based publishing cooperative that distributes agricultural information, recommends a minimum ventilation rate of 0.019 L/s/chick.(41) However, to obtain this minimum air flow, the vertical distance (VD) between containers should be about 8 centimeters,(42) which is much greater then the IATA recommended distance of 1 centimeter.(43) Ventilation rates around take-off and landing are significantly lower than during flight and pose a greater risk of rapidly increasing temperatures.(44) The problem is exacerbated in an aircraft due to the tight packing, restricted free volume around the transport containers, and the possibility of nearby mechanical equipment producing heat.(45)
Tanaka and Xin report oxygen shortages from a lack of ventilation that chicks experience in holding areas and cargo compartments of aircraft. Higher flow of air through the stacks of transport containers are recommended to alleviate this problem.(46) Research on heat tolerance and transport of day-old chicks has shown that two-compartment boxes with "about 20 chickens each and vertical spacing all around each stack will give the lowest weight loss and mortality."(47)
Conclusion
When transporting day-old chicks, extreme temperature ranges are detrimental to animal welfare, and, at excessively high and low temperatures, chicks can die in less than one hour. Reduced ventilation also adversely affects chicks. While good ventilation can help prevent high temperatures, it is not clear that current stacking configurations and spacing are adequate to promote proper ventilation.
According to the best research available to date, optimal conditions for day-old chick transport are: a temperature range of 24-25°C (75-77°F), relative humidity of approximately 65 percent, space allowance of 21 to 25 square centimeters per chick, and travel time from hatching no longer than 48 hours,(48),(49),(50) with some scientists advising even shorter travel times of 12 hours.(51) The temperature within the transport container should remain as close as possible to 31°C (88°F), though this may be difficult to ensure. Temperatures within densely packed commercial containers vary by several degrees due to poor ventilation. The transport boxes placed on the outer perimeter of a stack typically measure at different temperatures than those found towards the center of a stack, both vertically and horizontally.
Current container densities should be reviewed to improve ventilation through the transport crates in confined spaces. New research may also further clarify the importance of food and water access in reducing stress and mortality of chicks on long journeys or at extreme temperatures, but unless such work demonstrates that these resources are unnecessary, chicks should be transported with nutrient supplies to promote well-being.
(1) Mitchell MA and Kettlewell PJ. 2004. Transport of chicks, pullets and spent hens. In: Perry GC (ed.), Welfare of the Laying Hen (Cambridge, MA: CABI Publishing, pp. 361-74).
(2) European Food Safety Authority. 2004. The welfare of animals during transport: Scientific Report of the Scientific Panel on Animal Health and Welfare on a request from the Commission related to the welfare of animals during transport. Adopted March 30, 2004.
(3) Noy Y and Sklan D. 2002. Nutrient use in chicks during the first week posthatch. Poultry Science 81(3):391-9, citing: Romanoff AL. 1960. The Avian Embryo: Structural and Functional Development (New York: Macmillan, pp. 1042-81) and Sklan D and Noy Y. 2000. Hydrolysis and absorption in the intestine of newly hatched chicks. Poultry Science 79:1306-10.
(4) Bigot K, Mignon-Grasteau S, Picard M, and Tesseraud S. 2003. Effects of delayed feed intake on body, intestine, and muscle development in neonate broilers. Poultry Science 82(5):781-8, citing: Bigot K, Tesseraud S, Taouis M, and Picard M. 2001. Posthatch feeding and early development in broiler chicks. Productions Animales 14(4):219-30.
(5) Scientific Panel on Animal Health and Animal Welfare. 2004. Opinion of the Scientific Panel on Animal Health and Animal Welfare on a request from the Commission related to the welfare of animals during transport. The EFSA Journal 44:1-36.
(6) Scientific Panel on Animal Health and Animal Welfare. 2004. Opinion of the Scientific Panel on Animal Health and Animal Welfare on a request from the Commission related to the welfare of animals during transport. The EFSA Journal 44:1-36.
(7) Freeman BM. 1984. Transportation of poultry. World's Poultry Science Association Journal 40(1):19-30.
(8) Freeman BM. 1984. Transportation of poultry. World's Poultry Science Association Journal 40(1):19-30.
(9) Decuypere E, Tona K, Bruggeman V, and Bamelis F. The day-old chick: a crucial hinge between breeders and broilers. World's Poultry Science Journal 57:127-38.
(10) Qureshi AA. 1991. Losses due to dehydrated broiler chicks. World Poultry (Misset) 7(4):75-9.
(11) Xin H and Rieger SR. 1995. Physical conditions and mortalities associated with international air transport of young chicks. Transactions of the American Society of Agricultural Engineers 38(6):1863-7.
(12) Scientific Panel on Animal Health and Animal Welfare. 2004. Opinion of the Scientific Panel on Animal Health and Animal Welfare on a request from the Commission related to the welfare of animals during transport. The EFSA Journal 44:1-36.
(13) European Food Safety Authority. 2004. The welfare of animals during transport: Scientific Report of the Scientific Panel on Animal Health and Welfare on a request from the Commission related to the welfare of animals during transport. Adopted March 30, 2004.
(14) Bigot K, Mignon-Grasteau S, Picard M, and Tesseraud S. 2003. Effects of delayed feed intake on body, intestine, and muscle development in neonate broilers. Poultry Science 82(5):781-8, citing: Bigot K, Tesseraud S, Taouis M, and Picard M. 2001. Posthatch feeding and early development in broiler chicks. Productions Animales 14(4):219-30.
(15) Juul-Madsen HR, Su G, and Sørensen P. 2004. Influence of early or late start of first feeding on growth and immune phenotype of broilers. British Poultry Science 45(2):210-22.
(16) Juul-Madsen HR, Su G, and Sørensen P. 2004. Influence of early or late start of first feeding on growth and immune phenotype of broilers. British Poultry Science 45(2):210-22.
(17) Gonzales E, Kondo N, Saldanha ESPB, Loddy MM, Careghi C, and Decuypere E. 2003. Performance and physiological parameters of broiler chickens subjected to fasting on the neonatal period. Poultry Science 82(8):1250-6.
(18) Careghi C, Tona K, Onagbesan O, Buyse J, Decuypere E, and Bruggeman V. 2005. The effects of the spread of hatch and interaction with delayed feed access after hatch on broiler performance until seven days of age. Poultry Science 84(8):1314-20.
(19) Henken AM, van Der Hel W, Hoogerbrugge A, and Scheele CW. 1987. Heat tolerance of one-day-old chickens with special reference to conditions during air transport. Current Topics in Veterinary Medicine and Animal Science 44:261-87.
(20) Maiorka A, Kahlke F, and Morulis MSFA. 2006. Broiler adaptation to post-hatching period. Cienciaa Rural, Santa Maria 36(2):701-8.
(21) Mitchell MA and Kettlewell PJ. 2004. Transport of chicks, pullets and spent hens. In: Perry GC (ed.), Welfare of the Laying Hen (Cambridge, MA: CABI Publishing, pp. 361-74).
(22) Xin H and Harmon JD. 1996. Responses of group-housed neonatal chicks to posthatch holding environment. Transactions of the American Society of Agricultural Engineers 39(6):2249-54.
(23) Malheiros RD, Moraes VMB, Bruno LDG, Malheiros EB, Furlan RL, and Macari M. 2000. Environmental temperature and cloacal and surface temperatures of broiler chicks in first week post-hatch. Journal of Applied Poultry Research 9:111-7.
(24) Freeman BM. 1984. Transportation of poultry. World's Poultry Science Association Journal 40(1):19-30.
(25) Van der Hel W, Verstegen MWA, Henken AM, and Brandsma HA. 1991. The upper critical temperature in neonatal chicks. Poultry Science 70:1882-7.
(26) Mission BH. 1976. The effects of temperature and relative humidity on the thermoregulatory responses of grouped and isolated neonate chicks. Journal of Agricultural Science (Cambridge) 86:35-43.
(27) Randall WC. 1943. Factors influencing the temperature regulation of birds. American Journal of Physiology 139:56-63.
(28) Roberts D. 1978. Handling baby chick shipments. In: McWilliam AA (ed.), Animal Air Transportation: A Global Industry, Proceedings of the Fourth Annual International Meeting, Animal Air Transportation Association, November 6-9 (Toronto, Ontario: Animal Air Transportation Association, pp. 67-76).
(29) Xin H and Rieger SR. 1995. Physical conditions and mortalities associated with international air transport of young chicks. Transactions of the American Society of Agricultural Engineers 38(6):1863-7.
(30) Freeman BM. 1984. Transportation of poultry. World's Poultry Science Association Journal 40(1):19-30.
(31) Freeman BM. 1984. Transportation of poultry. World's Poultry Science Association Journal 40(1):19-30.
(32) Pinchasov Y and Noy Y. 1993. Comparison of posthatch holding time and subsequent early performance of broiler chicks and turkey poults. British Poultry Science 34(1):111-20.
(33) Roberts D. 1978. Handling baby chick shipments. In: McWilliam AA (ed.), Animal Air Transportation: A Global Industry, Proceedings of the Fourth Annual International Meeting, Animal Air Transportation Association, November 6-9 (Toronto, Ontario: Animal Air Transportation Association, pp. 67-76).
(34) International Air Transportation Association. 2006. Live Animals Regulations, 33rd Edition (Montreal: International Air Transportation Association).
(35) Mitchell MA and Kettlewell PJ. 2004. Transport of chicks, pullets and spent hens. In: Perry GC (ed.), Welfare of the Laying Hen (Cambridge, MA: CABI Publishing, pp. 361-74), citing: Ross Breeders. 1996. Producing quality broiler meat. Ross Broiler Management Manual; Meijerhof R. 1997. The importance of egg and chick transportation. World Poultry 13(11):17-8; Weeks C and Nicol C. 2000. Poultry handling and transport. In: Grandin T. (ed), Livestock Handling and Transport (Wallingford, UK: CAB International, pp. 363-84).
(36) Scientific Panel on Animal Health and Animal Welfare. 2004. Opinion of the Scientific Panel on Animal Health and Animal Welfare on a request from the Commission related to the welfare of animals during transport. The EFSA Journal 44:1-36.
(37) Mitchell MA and Kettlewell PJ. 2004. Transport of chicks, pullets and spent hens. In: Perry GC (ed.), Welfare of the Laying Hen (Cambridge, MA: CABI Publishing, pp. 361-74).
(38) Scientific Panel on Animal Health and Animal Welfare. 2004. Opinion of the Scientific Panel on Animal Health and Animal Welfare on a request from the Commission related to the welfare of animals during transport. The EFSA Journal 44:1-36.
(39) Freeman BM. 1984. Transportation of poultry. World's Poultry Science Association Journal 40(1):19-30.
(40) Hoogerbrugge A and Ormel HJ. 1982. Transport of day old chicks by air: mortality. Current Topics in Veterinary Medicine and Animal Science 18:139-46.
(41) Tanaka A and Xin H. 1997. Effects of structural and stacking configuration of containers for transporting chicks in their microenvironment. Transactions of the ASAE. 40(3):777-82, citing: Midwest Plan Service. 1990. MWPS-34: Heating, Cooling and Tempering Air for Livestock Housing (Ames, Iowa: Midwest Plan Service).
(42) Tanaka A and Xin H. 1997. Effects of structural and stacking configuration of containers for transporting chicks in their microenvironment. Transactions of the ASAE. 40(3):777-82, citing: Midwest Plan Service. 1990. MWPS-34: Heating, Cooling and Tempering Air for Livestock Housing (Ames, Iowa: Midwest Plan Service).
(43) International Air Transportation Association. 2006. Live Animals Regulations, 33rd Edition (Montreal: International Air Transportation Association).
(44) Hoogerbrugge A and Ormel HJ. 1982. Transport of day old chicks by air: mortality. Current Topics in Veterinary Medicine and Animal Science 18:139-46.
(45) Hoogerbrugge A and Ormel HJ. 1982. Transport of day old chicks by air: mortality. Current Topics in Veterinary Medicine and Animal Science 18:139-46.
(46) Tanaka A and Xin H. 1997. Effects of structural and stacking configuration of containers for transporting chicks in their microenvironment. Transactions of the ASAE. 40(3):777-82, citing: Midwest Plan Service. 1990. MWPS-34: Heating, Cooling and Tempering Air for Livestock Housing (Ames, Iowa: Midwest Plan Service).
(47) Henken AM, van Der Hel W, Hoogerbrugge A, and Scheele CW. 1987. Heat tolerance of one-day-old chickens with special reference to conditions during air transport. Current Topics in Veterinary Medicine and Animal Science 44:261-87.
(48) Mitchell MA and Kettlewell PJ. 2004. Transport of chicks, pullets and spent hens. In: Perry GC (ed.), Welfare of the Laying Hen (Cambridge, MA: CABI Publishing, pp. 361-74).
(49) Scientific Panel on Animal Health and Animal Welfare. 2004. Opinion of the Scientific Panel on Animal Health and Animal Welfare on a request from the Commission related to the welfare of animals during transport. The EFSA Journal 44:1-36.
(50) Juul-Madsen HR, Su G, and Sørensen P. 2004. Influence of early or late start of first feeding on growth and immune phenotype of broilers. British Poultry Science 45(2):210-22.
(51) Mitchell MA and Kettlewell PJ. 2004. Transport of chicks, pullets and spent hens. In: Perry GC (ed.), Welfare of the Laying Hen (Cambridge, MA: CABI Publishing, pp. 361-74), citing: Mitchell MA, Kettlewell PJ, Carlisle AJ, Hunter RR, and Manning T. 1996. Defining the optimum thermal environment for the transportation of one-day-old chicks: physiological responses during transport simulations. British Poultry Science 37(Supplement):S89-S91.
