Role of socialization, stress and sex of chickens on response to anesthesia and on response to an organophosphate neurotoxicant.

The influence of socialization of chickens on response to exogenous substances in the presence and absence of stress was examined. Chickens of both sexes were habituated to human beings (socialized) by being talked to and offered food from the hand of the caretaker. After 19 w, half the socialized group and half the unsocialized group were subjected to stress (loud noises for 120 sec twice daily) for 2 w. At the end of this period, response to 37 mg pentobarbital/kg iv was evaluated by length of sleeping time. Males slept longer than females, and males that were socialized but not stressed slept significantly longer than other males. Stress and socialization did not significantly affect pentobarbital sleeping time in females. This indicated that response to pentobarbital was dependent on sex and on socialization, with the most notable effects occurring in socialized males. Socialized and nonsocialized, stressed and unstressed male and female chickens were also administered a single po dose of 360 mg tri-ortho-tolyl phosphate (TOTP)/kg. This organophosphorus ester induced a delayed neuropathy that caused ataxia in all the chickens. The ataxia was significantly more pronounced earlier in males than in females, although the sex difference became insignificant 18 d after dosing. Socialized chickens were ultimately more affected. Noise stress did not affect TOTP-induced ataxia. This indicated that response to an organophosphate neurotoxicant was also dependent on sex and socialization, with the most notable effects again seen in socialized males. Response to endogenous substances in chickens depends both on sex and on familiarity to humans.