Hormonal usage in canine theriogenology (Proceedings)
Failure of corpus luteum formation or function
Bitches with the history of subfertility or infertility should be examined for pregnancy at 25 days following the last breeding using ultrasonographic examination or palpation depending upon the animal and the examiner. Ultrasonographic examination is superior in that the owner also can visualize the fetuses. Serum progesterone concentrations should be determined in bitches that are nonpregnant or in pregnant ones when there is reason to believe fetal resorption or abortion has occurred in the past with no other apparent reason.
Progesterone concentrations in nonpregnant bitches below 5 ng/ml indicate possible luteolysis has occurred. Concentrations less than 1 ng/ml indicate ovulation did not occur or very early luteolysis did occur. In bitches where premature luteolysis is suspected or differentiation between the two conditions is necessary, serial progesterone concentrations at 5 to 7 day intervals through day 25 or further into gestation is recommended. Ovulation failure is an unlikely cause of lowered progesterone if estrous behavior, luteinizing hormone concentrations, vaginal cytology and/or vulvar discharge and swelling were normal. Clients must always be advised before starting progesterone supplementation, that progesterone supplementation in bitches during pregnancy may induce masculinization of canine fetuses.Estrus suppression
Ovaban is not indicated or recommended for use in breeding bitches. It is a progestational compound and as such does increase the possibility of pyometra or cystic endometrial hyperplasia. Mibolerone is an androgenic hormone used for estrus suppression. It has the potential, as do all androgenic steroids of inducing hepatotoxic lesions but this has not been reported in the canine with recommended use. Its primary side effects include increased lacrimation in toy breeds and clitoral hyperplasia with prolonged usage. Although not approved for use in breeding bitches. the author routinely uses it for suppression of estrus for 6 to 10 months or at times longer, and had a non-breeding animal on medication for 12 years with no adverse side effects.
Desorelin implants down regulate the production of FSH from the pituitary. Synthetic GnRH preparations given at high doses cause a decreased production of FSH.
Cystic ovaries are primarily demonstrated by prolonged proestrus and/or estrus. Signs of both occurring repeatedly multiple times during the same estrus are possible, It may be called a split heat or cystic ovarian disease but it is the same condition. Based upon information available in other species, the prolongation of a mature oocyte within the follicle reduces the probability the oocyte will be fertile and that ovulation will be normal. For this reason and because this condition can persist for 6 to 8 weeks if untreated, the author prefers to treat accordingly with human chorionic gonadotropin as soon as possible and not breed the bitch. The success of this therapy is extremely high with over 90% of the animals responding to a single treatment. The bitches cease the proestrus or estrus within 5 to 10 days. Recommended dosage is 500 to 1000 units administered intra-muscularly. GnRH has also been used at a dosage of 50 ug administered intramuscularly. Since the proestrus and estrus were prolonged it is advisable to always examine these animals at 25 to 35 days following treatment for the possible development of pyometra. The treatment does not cause the pyometra, the prolonged exposure to the estrogen predisposes to the condition.