U.S. Department of Agriculture: Animal and Plant Health Inspection Service


Date of this Version

August 2002


Published by Journal of Controlled Release 85 (2002) 135-143. Permission to use. www.elsevier.com/locate/jconrel.


Sixty-three mallards were fed one of ten poly(methyl methacrylate) based synthetic grit formulations containing varying concentrations of a proposed wildlife contraceptive (nicarbazin), plasticizer (acetyl tributylcitrate) and/or cross-linking agent (1,4-butanediol diacrylate). Release characteristics of the contraceptive agent were monitored for the purpose of developing a contraceptive formulation for control of pest waterfowl in urban settings. The addition of plasticizer increased the erosion rate (t1/2=0.97-2.85 days), cross-linking the polymer matrix slightly decreased the erosion rate (t1/2=4.45-5.05 days) and increasing the concentration of the contraceptive agent increased the erosion rate (t1/2= 3 . 3 and 9.9 days at 60% and 7.5% active ingredient. respectively). The larger and smaller grit pieces had longer half lives at 11.0 and 11.6 days, respectively while the mid sized grit had a half life of 4.95 days. Control grit had a half life of 12.7 days based on weight loss. Analysis of blood and feces for monitoring release from the grit and approximate indirect plasma levels of the active ingredient proved feasible.