Pharmacokinetic parameters of [14C]diflubenzuron, N-([(4-chlorophenyl) amino]-carbonyl)-2,6-difluorobenzamide, in White Leghorn (WL) egg-production chickens and Rhode Island Red/Barred Plymouth Rock (RIR/BPR) meat-production chickens after single 1-mg/kg intravenous and single 5-mg/kg oral doses were investigated to explain a breed-related egg residue-level difference (higher in WL chickens) after daily oral administration. Analysis of [14C]diflubenzuron concentration in blood versus time indicated similar two-compartment models for each bird type. [14C]Diflubenzuron elimination half-lives from the blood of WL and RIR/BPR chickens were 14.7 and 8.4 h, respectively. Absorption of [14C]diflubenzuron after a single 5-mg/kg oral dose was both faster and more complete in RIR/BPR chickens. Absorption rate constants were 0.046 h-1 and 0.192 h-1 for WL and RIR/BPR hens, respectively. It is concluded that the breed-related egg residue difference was due to a larger peripheral compartment volume in RIR/BPR hens.

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