ANESTRUS IN MARES - EXPERIENCES USING OVUPLANT, A SHORT-TERM IMPLANT OF THE GNRH ANALOG DESLORELIN, FOLLOWING IMPLANTATION WITH CIDR-B, A PROGESTERONE RELEASING INTRAVAGINAL DEVICE

On a single farm in south-east Queensland, 25% of 350 Standardbred mar es were anoestrous after October 15th. Over the period of examination, 87 mares (15 maiden, 49 barren and 23 lactating) failed to produce ov ulatory follicles in the absence of a functional corpus Luteum and the y were treated with intervaginal progesterone releasing devices (CIDR- B) for various periods until a follicle of at Least 30 mm had develope d. Fifty seven of 58 (98%) mares that had a follicle Larger than 30 mm at the end of the progesterone treatment ovulated after an injection of 2500 units hCG was given between zero and six days after withdrawal of the device; 37 (65%) of these were pregnant at 14-17 days. Twenty six mares failed to develop a follicle of at Least 30 mm even after pr olonged periods of progesterone treatment. Seven of these ovulated and seven failed to ovulate following removal of CIDR-B and administratio n of hCG. The other 12 mares were given a short-term implant of deslor elin: nine ovulated, seven were inseminated and four (57%) became preg nant. This preliminary study indicates a possibly satisfactory method of treating persistently anoestrous mares.