CASE 9. Contraception in a female wolf
Case Information: You are presented with a timberwolf from the local zoo. The zookeeper likes to house the wolves as a pack for social reasons but that means the dominant females are much more likely to be bred than are the subordinate females. The wolf presented to you is the dominant female; she is 7 years of age and has not had a litter in the last two years, despite having been bred by a known fertile male. The zookeeper wants you to treat her with something that will prevent her from coming into heat so the males will be drawn away from her and toward the younger, healthier subordinate bitches. She is interested in your using an analogue of GnRH.
Question:
What is the mechanism of action of GnRH in suppressing estrus?
Answer:
Repeated administration of GnRH results in decreased production of LH and FSH due to down-regulation of GnRH receptors in the pituitary.
Question:
Is this an appropriate drug for this situation?
Answer:
It may not be. Behavior issues = the dominant male wolf or wolves may choose
not to breed subordinate females, even if the dominant female is not cycling.
Therapeutic issues = administration of GnRH initially may be associated with
induction of estrus, as it will stimulate production of LH and FSH in the short-term.
That means this wolf will go into heat and may again be bred despite your best
intentions. For a discussion of induction of estrus in dogs, see Kutzler,
MA. Induction and synchronization of estrus in dogs, Theriogenology 2005;64(3):766-775.