Whole-carcass residues of the rodenticide difenacoum in anticoagulant-resistant and -susceptible rat strains (Rattus norvegicus)

Environ Toxicol Chem. 2005 Feb;24(2):318-23. doi: 10.1897/04-022r.1.


The present study investigated the whole-carcass residue carried by resistant and susceptible laboratory rat strains following 5, 10, or 20 d of feeding on a diet of 25 mg difenacoum/kg bait. The mean whole-carcass residue of difenacoum was determined by high-performance liquid chromatography to be between 0.52 and 0.74 mg/kg body weight in all three rat strains tested. These values were considerably lower than some comparable data previously reported for other species and second-generation rodenticides as well as from mathematical models. The whole-carcass residue of extractable (i.e., nonrefractory) parent compound carried by highly resistant rats fed for 20 d (0.74 mg/kg body wt) is unlikely to present a significantly increased risk to predators compared to the amount carried by susceptible rats after 5 d of feeding (0.52 mg/kg body wt). However, resistant rats are more likely to be available for predation and to be carrying a whole-carcass residue of anticoagulant throughout the duration of a control program.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 4-Hydroxycoumarins / administration & dosage
  • 4-Hydroxycoumarins / toxicity*
  • Animal Feed
  • Animals
  • Anticoagulants / administration & dosage
  • Anticoagulants / toxicity*
  • Blood Coagulation Tests
  • Body Weight / drug effects
  • Chromatography, High Pressure Liquid
  • Drug Resistance
  • Pesticide Residues / metabolism
  • Pesticide Residues / toxicity*
  • Rats
  • Risk Assessment
  • Rodenticides / administration & dosage
  • Rodenticides / toxicity*
  • Time Factors


  • 4-Hydroxycoumarins
  • Anticoagulants
  • Pesticide Residues
  • Rodenticides
  • difenacoum