Modification of triorthotolyl phosphate toxicity in chickens by stress.

Chickens housed for 4.5 months in an environment of either low social stress or high social stress were administered triorthotolyl phosphate (TOTP) 180 mg/kg po. Clinical signs of delayed neuropathy were less in the low social stress group, unless moved to a high stress environment 24 hr before TOTP administration. Neurotoxic esterase activity was less than 20% of control values in all treatment groups. Birds from the low social stress group moved 24 hr prior to TOTP were more susceptible to inhibition of brain and liver cholinesterase activities following organophosphate administration. Liver microsomal enzyme activities (O-demethylase and aniline hydroxylase) were lowest in unmoved low social stress birds after TOTP, possibly protecting these birds from delayed neuropathy by reducing conversion of this organophosphate to its active metabolite.