The role of dicofol metabolites in the eggshell thinning response of Ring Neck Doves

Abstract

Residue data is presented from shell thinning studies in Ring Neck Doves (Streptopelia risoria) fed 33 mg/kg, or 10 mg/kgp,p′ dicofol or the dicofol metabolite 1,1-bis(4-chlorophenyl)2,2 dichloroethanol (p,p′ DCD) at 10 and 32 mg/kg for approximately 90 days. The metabolism and storage of dicofol and dicofol metabolites in breeding females is examined. Concentrations ofp,p′ dicofol, DCDp,p′ dichlorobenzophenone (p,p′ DCBP),p,p′ dichlorobenzydrol (p,p′ DCBH), and 1,1-bis(4-chlorophenyl)-2,2 dichloroethylene (p,p′ DDE) were determined in liver, fat, heart, brain, oviduct and yolk of doves. The major metabolite was DCD. Doves exposed to DCD alone did not produce thinned eggshells at either dose. DCD was poorly metabolized by doves to DCBP and DCBH. DDE was present but in concentrations far below other OCs and was not a metabolite of dicofol. Doves had two metabolic routes for transforming dicofol to more water soluble metabolites, reduction to DCD and oxidation to DCBP with subsequent formation of DCBH. The formation of DCBH was limited by the rate of DCBP formation. Yolk residues of DCBP indicated individual doves varied in their ability to produce DCBP. DCBP accumulation in yolk over time was correlated with individual doves' eggshell thinning response over time of treatment. Doves with low rates of DCBP accumulation in yolk had greater declines in shell thickness per day of dicofol treatment. It is concluded that the dicofol metabolites DCD, DCBP, and DCBH are less toxic than dicofol to eggshell formation in ring neck doves.