altrenogest and deslorelin

To date, there has been limited research on manipulation of the estrous cycle in endangered equids. The objectives of this study were to assess the efficacy of using combinations of: (a) oral altrenogest and PGF2α, and (b) injectable altrenogest and PGF2α for manipulation of ovarian activity in Przewalski's mares. Reproductive cycles were monitored by assessing follicular changes with rectal ultrasound and changes in urinary steroid hormones. In Study 1, five cycling mares were treated with oral altrenogest (n=11 cycles) for 14 days. In Study 2, cycling mares were treated with oral altrenogest for 12 days (n=5 cycles; n=5 mares) or a single injection of biorelease altrenogest (n=10 cycles; n=6 mares). In all study groups, PGF2α was given 2 days before cessation of progestagen treatment. In Study 1, mares responded in six of 11 cycles (54%) where treatment occurred with normal ovarian follicular development post hormone therapy. In Study 2, mares responded in four of five (80%, oral altrenogest) and eight of 10 (80%, injectable altrenogest) cycles with the development of an ovulatory follicle. With the use of injectable altrenogest, there was an obvious suppression of urinary estrogens and progetsagens. These results indicate that manipulation of the estrous cycle of Przewalski's mares can be achieved by administering oral (12 days) or injectable form of altrenogest in conjunction with PGF2α. Findings in the present study may have long term application for the development of timed artificial insemination as a genetic management tool for this critically endangered equid.

Topics: Administration, Oral; Animals; Dinoprost; Estrogens; Estrous Cycle; Female; Horses; Injections, Intramuscular; Ovarian Follicle; Progestins; Time Factors; Trenbolone Acetate; Triptorelin Pamoate

Practical estrus synchronization schemes are needed for mares. The Ovsynch synchronization protocol for cattle involves the administration of gonadotropin-releasing hormone (GnRH) to induce ovulation or luteinization of dominant follicles during the luteal phase and prostaglandin 7 days later to cause regression of any luteal tissue and development of a preovulatory follicle. An Ovsynch-type synchronization program potentially could be developed for horses if luteinization or ovulation of diestrous follicles occurred in response to GnRH treatment. The objective of this study was to determine if administration of the GnRH agonist, deslorelin acetate, on Day 8 or 12 postovulation would induce luteinization or ovulation of diestrous follicles in the mare. The model used was cycling mares maintained in an artificial luteal phase by administration of a synthetic progestin following prostaglandin-induced luteal regression. On the day of ovulation, 21 light horse mares were randomly assigned to one of three groups: (1) no GnRH, altrenogest from Days 5 to 15 postovulation with prostaglandin on Day 15; (2) GnRH on Day 8, altrenogest from Days 5 to 15 with prostaglandin given on Day 6 to induce luteolysis of the primary corpus luteum, an implant containing 2.1mg of deslorelin acetate inserted on Day 8 and removed on Day 10, with a second prostaglandin treatment on Day 15; (3) GnRH on Day 12, altrenogest from Days 9 to 19, prostaglandin on Day 10, a deslorelin acetate implant injected on Day 12 (subsequently removed on Day 14), and a second dose of prostaglandin administered on Day 19. Follicular development was monitored every other day from Day 5 until a 30-mm sized follicle was observed, and then daily to detection of ovulation. Serum progesterone concentrations were determined daily for 12 consecutive days. Progesterone concentrations in Group 1 remained elevated until approximately Day 12 postovulation. Prostaglandin administration on Day 15 resulted in complete luteolysis in all seven mares. In Group 2, progesterone concentrations in six of seven mares declined to baseline after prostaglandin treatment. No increase in serum progesterone was noted in any of the six mares that were given GnRH on Day 8, including three mares that had diestrous follicles > or =30mm in diameter at the time of treatment. Similarly, progesterone concentrations in six of seven mares in Group 3 declined to baseline after prostaglandin and there was no increase in progesterone after adm

Topics: Animals; Cloprostenol; Diestrus; Drug Implants; Estrus Synchronization; Female; Gonadotropin-Releasing Hormone; Horses; Luteinization; Luteolysis; Ovarian Follicle; Ovulation; Progesterone; Trenbolone Acetate; Triptorelin Pamoate