Effect of adrenal blocking chemicals on the responses of chickens and turkeys to environmental stressors and ACTH.
An adrenal blocker, 1,1dichloro-2,2-bis/p-chlorophenyl/ethane, was most effective when given intramuscularly, at a dose rate of 16 or 14 mg/kg of body weight, the technical or reagent chemical, respectively (P<0.001). The optimal dose for meryrapone was 500 mg/kg feed. Following exposure to a variety of Stressors treated chickens and turkeys had heterophil/lymphocyte ratios which were lower than those of the uninjected controls. The optimal doses were effective over a wide range of body weights (0.35 to 5.2 kg). Blocking began within 12 h after injection and lasted for at least 77 days. Repeated doses were not additive. Blockers did not suppress body weight gain. The magnitude of the blocking effect increased with increasing H/L ratios among the controls and was ineffective in unstressed chickens.
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Department of Large Animal Clinical Sciences, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Polytechnic Institute, State University, Blacksburg, Virginia, USA.