|Kahl, Stanislaw - Stass|
|LEACH, JR., R.|
Submitted to: Poultry Science Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 7/15/2002
Publication Date: 8/10/2002
Citation: McMurtry, J., Yahav, S., Brocht, D., Ashwell, C., Rosebrough, R., Kahl, S., Leach, R. 2002. Endocrine and metabolite adaptations in the thermoconditioned chicken in response to high ambient temperature. Poultry Science. v. 81:214.
Technical Abstract: Prior research has shown that early in life thermoconditioning (TC) results in improvements in performance and thermotolerance. This study was conducted to assess the endocrine and metabolite response to high ambient temperature by TC chickens. On day 3 post hatch, TC was induced by exposing male broiler chicks to an ambient temperature of 37.5 C for 24 hrs. Control (C) chicks were maintained at brooder temperature of 32 C. Blood samples were taken at the end of TC and 21 days of age. At 42 days of age both groups were exposed to an ambient temperature of 36.5 C (challenge phase). Blood samples were drawn prior to and at intervals during the challenge phase. All blood samples were analyzed for various hormones and metabolites. Free access to feed and water was provided. Overall, exposure to elevated ambient temperature increased plasma corticosterone, glucagon, IGF-II, and leptin, while triiodothyronine and insulin were decreased. However, the extent of the hormonal response was significantly different between the TC and C groups, with the response being suppressed in the TC birds compared to the C group. Plasma IGF-I and thyroxine were unaffected by heat challenge. In TC chickens, hepatic deiodinase activity remained unchanged during the challenge phase, whereas in the C group, activity was significantly increased. Plasma free fatty acids were increased in both groups by heat challenge. Uric acid was increased in C birds, but remained unchanged in the TC chickens. Mortality was reduced by 50% in the TC groups compared to that in the C group. It is evident from this study that the physiological and biochemical response to heat stress is ameliorated in TC chicks, and that this change imparts some ability to adapt to elevated ambient temperatures. However, it remains to be determined how and where the control mechanisms are changed to enable the TC chicken to adapt to heat stress.