Induction of Ovulation

  • Ovulation can be induced by vaginal stimulation with a glass rod, thermometer, or Concannon even adapted an electric toothbrush! You must give multiple stimulations at least 2 hours apart to induce a sufficient LH peak. Also, listen for the 'aftercry' to ensure complete stimulation.
  • A specific device marketed by Globanimal called the 'Ovulator' is marketed as an instrument to induce ovulation.
  • This company was trying to enforce a patent on ovulation induction via vaginal stimulation. The web site no longer works, and I have not tried to call them.


Click here to view a glass rod being used to induce ovulation.
Right click on the frame to start.

Click here to view "The Toothbrush"
Right click on the frame to start.

  • Ovulation can also be induced with exogenous hormones.
  • Administration of GnRH or LH after mating can be used to increase the likelihood of ovulation. Both stimulate ovulation by bypassing the vaginal/hypothalamic neural pathway.


  • According to one report, administration of 25 ug of GnRH on the second day of estrus resulted in all mature follicles present ovulating in all queens treated.
  • Unlike hCG, GnRH administered in conjunction with natural mating did not enhance ovulation. 

Human chorionic gonadotrophin

  • Human chorionic gonadotrophin (hCG, Follutein, Solvay Veterinary Inc., Princeton, NJ) has LH-like activity and can be used as well as GnRH to induce ovulation. 
    • The results of two reports suggest that a dose of 500 IU hCG on day 1 or days 1 and 2 of estrus achieved maximal ovulation rates. 
    • With lower doses, all queens ovulated but ovulation rates per queen were less than 100%. 
    • hCG, administered at a dose of 250 IU on days 2 and 3 of estrus, and coupled with mating three times per day at three hour intervals for the first three days of estrus resulted in a doubling in the number of corpora lutea formed. 
    • Unlike hCG, GnRH administered in conjunction with natural mating did not enhance ovulation. 
    • hCG administration may be useful in cases where the male has a low libido and where a sufficient number of copulatory stimuli are not achieved.
Induction of Estrus
  • Estrus can be induced in the queen using follicle stimulating hormone (FSH,FSH-P, Schering Corp., Kenilworth, NJ)7,22 or pregnant mare serum gonadotrophin (PMSG, eCG).

P.G. 600

  • Currently, PMSG (eCG) is commercially available in the United States only in combination with hCG (P.G.600 Intervet America Inc., Millsboro, DE). The effect of using hCG combined with PMSG in an estrus induction scheme is unknown.


  • The most successful protocol for induction of estrus using currently available products administers 2.0 mg FSH IM daily until estrus, but for not more than 5 days.
  • Using this protocol, normal fertility was observed in mated queens after estrus induction.
  • Prolonged administration of FSH resulted in follicular ovarian cysts which subsequently failed to rupture.
  • Although they stimulated mature follicular development, higher doses of FSH given as a single injection, resulted in inconsistent sexual receptivity.
  • Some queens, especially those under 1 year of age, appear to be sensitive to ovarian hyperstimulation by exogenous gonadotrophins.
  • Queens experiencing an induced estrus may have an increased number of both unovulated follicles and corpora lutea than queens having a natural estrus.
Estrus Prevention or Suppression


  • Practitioners are at times asked to prevent or suppress estrus in the queen.
  • No approved drugs exist for this purpose.
  • Cases of pyometra and cystic endometrial hyperplasia associated with the use of progestogens in queens have been reported. These side effects however, are not as common in queens as they are in bitches.


  • Megestrol acetate, (Ovaban, Schering Corp., Kenilworth, NJ) though not approved for use in cats, has been used for both estrus prevention and suppression. When begun during seasonal anestrus, the administration of 2.5 mg/wk for up to 18 months.
    • During the breeding season, begin treatment during interestrus: 2.5 mg daily per os, can be given for up to 60 days prevented a return to estrus. During the breeding season, 2.5 mg given daily beginning during the interestrous interval for up to 60 days similarly delayed a return to estrus.
    • When suppression of estrus is desired, a dosage of 5 mg daily for 3 days or until signs of estrus ceases should be given. In this case, therapy is continued at a dose of 5 mg/week for 10 weeks or 2.5 mg/day for 60 days.
    • The return of estrus was successfully delayed during treatment and for 1 to 3 months after cessation of treatment.
    • Other than weight gain, no serious side effects of megestrol acetate were observed.
    • More recently, significant adrenal cortical suppression has been reported with the use of megestrol acetate.
    • The queen should be allowed to have a normal estrus without hormonal manipulation before retreatment.


  • Mibolerone, an androgenic steroid, is effective in preventing estrus in queens. Serious side effects, however, preclude its use in cats. Possibly fatal hepatic disease; changes in thyroid function, serum cholesterol, thyroid histology and weight; and slight masculinization noted by clitoral hypertrophy and thickening of the cervical dermis were observed.
  • Not available at this time.

Delmadinone acetate
  • Although not currently available in the U.S., delmadinone acetate (DMA) offers promise for estrus control in the queen.
  • It was found to be safe and effective when administered for up to 36 months.
  • For estrus prevention, DMA can be administered orally once a week or injected subcutaneously every 6 months.
  • For estrus suppression, DMA is administered orally once daily for 6 days or in-jected SC once or twice in a 24 hour period.
  • No short or long term side effects were noted with use of DMA in cats.

  • Permanent estrus prevention, of course, is best achieved by ovariohysterectomy.
  • No undesirable side effects, other than possible weight gain if fed ad libitum, have been associated with ovariohysterectomy in queens.
  • Ovariohysterectomy may be performed on prepubertal kittens as young as 7 weeks of age. 
    • At this age, the procedure is relatively simple and recovery is rapid compared to older animals. 
    • No adverse signs have been seen when compared to performing gonadectomies at an older age. 
    • Neutering male cats this age results in no smaller penis than in toms neutered at an older age. 

contributed by Bruce E Eilts modified 27 July 2006

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contributed by Bruce E Eilts on 25 September 2012


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