Contributors: David Godfrey, Carlos Pinto
Species: Feline | Classification: Miscellaneous
- Temporary prevention of estrus is often requested by pet owners.
Reasons for estrus suppression
- Cats are induced ovulators, meaning they typically ovulate only when mated. When not mated, female cats may then cycle fairly frequently every 10-14 days - a period called interestrus - giving the impression the queens are "always" in estrus.
- To prevent (undesirable) overt signs of estrus in cycling queens: rolling, rubbing, vocalization, etc.
- To prevent undesirable male behavior of tom cats living in close proximity with cycling queens: vocalization, risk of increased aggression among cats, frequent spraying, etc.
- Estrus suppression may also be warranted because of illness, immaturity or to accommodate scheduled breeding plans.
Neutering should be performed on animals not needed for future breeding.
- There is no completely satisfactory method of preventing estrus.
Induction of a false pregnancy
- The cat is an induced ovulator. Unmated cats will then enter a subsequent estrus after a short interestrus period.
- Inducing ovulation will result in the formation of a corpus luteum. The female cat will not show behavioral signs of estrus during the ensuing diestrus period. The induced "false pregnancy" Pseudopregnancy lasts approximately 40-45 days.
- Ovulation may be induced by allowing mating by a vasectomized male. However, keeping a male cat for this purpose is rarely practical.
- They would have the same requirements of housing and health care as a fertile stud cat.
- Some neutered males will have enough libido to perform some sort of mating behavior that may be adequate to stimulate ovulation. Expecting that a neutered male will induce ovulation in cycling females is an unreliable method of estrus control/suppression.
- Manual stimulation of the cranial vagina has been advocated and first reported in 1934. Use of a glass rod or moistened cotton bud have been advised. However, this is potentially dangerous and is certainly difficult, especially if performed on a poorly restrained cat at home.
- Anecdotally, it seems that some cats seem to be induced to ovulate by vigorous petting of the rear half of the body to mimic the male behavior during mating. This is a practical method for owners to try at home but ovulation response to this approach may be highly variable. Ovulation is thought to be linked with the fury response-after normal mating the cat suddenly turns around and attacks the male.
The owner needs to be prepared for this potential female reaction when attempting to induce ovulation by manual stimulation.
- The after-reaction exhibited by the queen after mating (rolling, licking, rebuffing the male) can be used as an indication that manual stimulation has been sufficient to simulate mating. Many queens will not ovulate in response to a single stimulation and may require 3-4 such episodes to release sufficient luteinizing hormone (LH) to ovulate (see Concannon et al,1980).
- For many queens the only practical alternative is the use of pharmacological agents.
- Proligestone Proligestone (100 mg for a cat weighing on average 3 kg SC at sequential intervals of 3,4 and 5 months, and at intervals of 5 months thereafter) and medroxyprogesterone acetate Medroxyprogesterone (25-100 mg IM every 6-12 months) are long-lasting injection preparations to suppress or prevent estrus. In one study, administration of 30 mg (SQ) of proligestone to interestrus queens resulted in //www.vetlexicon.com 8 months of estrus suppression.
A major disadvantage of long-lasting injections is the inability to withdraw the agent if an adverse effect occurs.
- Megestrol acetate Megestrol acetate is an oral formulation that has been shown to be effective at a daily dose of 5 mg for 5 days and then once weekly.
- Mibolerone is an oral synthetic androgen that prevents estrus when administered at a dose of 50 ug per cat daily.
- Pseudopregnancy state can also be induced with GnRH Gonadotrophin releasing hormone (25 ug IM) or gonadotropins to trigger ovulation (250 IU) human chorionic gonadotropin Chorionic gonadotrophin). Repeated pseudopregnancy conditions may predispose female cats to pyometra Pyometra.
Many breeders find that doses lower than those recommended by the manufacturers are successful, especially for follow-up doses to maintain estrus suppression.
- Side effects that have been associated with the use of these pharmacological agents include:
- Not all these conditions have been proven to be caused by these agents however the owners should be informed about these issues.
- Serious problems can be seen even after short-term use with oral progestagens.
- Difficulty of surgery.