LEUPROLIDE ACETATE CAN REVERSIBLY PREVENT EGG-LAYING IN COCKATIELS (NYMPHICUS-HOLLANDICUS)

Leuprolide acetate acts as a superactive gonadotropin-releasing hormon e (GnRH) agonist in mammals. Its administration to humans in a depot f ormulation (Lupron Depot 3.75 mg; TAP Pharmaceuticals, Deerfield, IL) consisting of microspheres suspended in a diluent of carboxymethyl cel lulose and other elements leads to an initial increase in serum gonado tropin levels followed by a prolonged suppression of approximately 1 m onth's duration. To test whether it might act in cockatiels to prevent egg laying, we administered Lupron Depot to groups of pairs (at least 6 pairs/group) stimulated to reproduce by provision of nest boxes and exposure to sexually stimulatory daylengths (15:9 L:D). A single intr amuscular injection of Lupron Depot, calculated to achieve a daily rel ease rate of 0 (control; diluent only), 17, 52, or 156 mug/kg/day of l euprolide acetate, was administered on day 0, when birds received nest boxes and after daylength had been stepwise increased. Egg production began on day 12 in the 0 and 17 mug dose groups, and on day 31 in the groups receiving the higher doses. Number of eggs per clutch, candled fertility, and percent hatchability were not significantly different among the groups. In a separate experiment in which leuprolide was adm inistered prior to photostimulation and nest box presentation, nest-in spection behavior was not prevented. We conclude that a single injecti on of Lupron Depot is effective in reversibly preventing egg laying in cockatiels. (C) 1994 Wiley-Liss, Inc.