Equis ISSN 2398-2977

Reproduction: management - female

Contributor(s): Jean Pierre Held, Graham Munroe, Jonathan Pycock, Vetstream Ltd, Elaine Watson


  • The main objectives of managing mares reproductive function is to maximize fertility, minimize risk to mare/stallion, control the incidence of infection, ensure the efficient use of the stallion and minimize neonatal losses.
  • Major obstacles to these objectives are:
    • Mares are seasonal breeders and in some breeds are required to be in full ovulatory estrus before the natural onset of their seasonal cyclical activity.
    • Brood mares are also selected not on the basis of reproductive performance but on the athletic performance of themselves and their offspring.
    • Failure to detect estrus and determine optimal time for breeding.
    • Poor semen quality.
    • Failure to identify and treat reproductive abnormalities in mares.
    • Broodmares undergo a number of ancillary tests and extra management procedures to increase the likelihood of producing a live foal.
    • Management plays a vital role to the successful fertile outcome and veterinarians should be familiar with an individual mare's cyclical characteristics.

Teasing is a vital function in any breeding program and a number of methods are available.

  • Routine, logic and consistent reproductive monitoring of individual mares on stud farms is an essential part of modern management.

For further information on prevention and control of diseases associated with breeding mares in the UK see the Horserace Betting Levy Board's  Codes of Practice .

Breeding history



  • Cornerstone of routine stud farm management.
  • Keen, sensible teaser stallion.
  • Devote time and patience for each mare to be teased properly.
  • Record all responses.
  • Remember all mares are individuals - get to know variations.
  • Many different techniques including individual, group or free teasing are available.

Physical examination

  • Examination of the internal and external genitalia at estrus and may utilize speculum   Female: vaginoscopy  , ultrasonographic and fiberoptic   Uterus: endoscopy  examinations dependent on maiden, barren or foaling status   Female: vaginoscopy  .
  • Hormonal monitoring   Endocrine: hormone assay - female  in conjunction with palpation   Urogenital: rectal palpation  and ultrasonography may elucidate cyclical activity and explain teasing behavior.
  • Routine palpation of ovaries   Urogenital: rectal palpation  is usually carried out every 48 h when the mare is in estrus unless the stallion has known short-lived sperm in which case the interval between examinations may be 12 or 24 h apart. Artificial insemination   Reproduction: artificial insemination  with frozen semen will also require more frequent examinations.
  • Examination again at 48 h post-mating evaluates the ovulatory status of the ovary and assess any fluid present in the uterus and necessity for rebreeding or for an early check for twins if multiple corpora lutea are present.

Diagnostic aids

  • Progesterone profiles  Endocrine: hormone assay - female  :
    • Performed weekly will pick up the spike indicating the first ovulation of the season. Progesterone >4 ng/ml. Can be used in other situations.
  • Endometrial smear  Endometrium: biopsy  :
    • Cytology of cells collected off the cap of a guarded swab enables the detection of polymorphonuclear leukocytes in acute endometritis. Interpretation of swabs collected for bacteriology is more accurate when combined with cytology.
  • Bacteriology  Endometrium: bacteriology  :
    • Pre-mating swabs may be performed, according to the HBLB Code of Practice in the UK, for the prevention of venereal diseases and their spread.
    • Results of routine pre-breeding bacterial cultures must be critically evaluated as many positive results are due to swab contamination.
    • Swabs (clitorial and endometrial) will also be taken from mares that return after covering or show vaginal discharge, particularly in areas where CEM has been reported.
  • Pregnancy diagnosis:
    • Can be performed by ultrasonography from 14-16 days, when twins are more readily monitored and can be eliminated by squeezing. Repeat at 27 days and again for certification of pregnancy at 45 days   Fetus: pregnancy - head - ultrasound  .
    • Sexing of fetus may be possible >60 days   Fetus: twin abortion 01 - pathology  .
    • More frequent scans may be indicated if endometrial cysts, fibrosis   Endometrium: fibrosis  or hypoplasia   Endometrium: hypoplasia  are suspected and if fluid accumulates in the uterus.
    • Hormonal analysis for pregnancy diagnosis   Endocrine: hormone assay - female  .
Print off the Owner factsheets on Foaling - what you need to know and The pregnant mare - health and well-being to give to your clients.

The maiden mare

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The barren mare

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The pregnant mare

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Further Reading


Refereed papers
  • Recent references fromPubMed.
  • Meyers P J (1993)Methods of controlling and synchronizing oestrus in the mare. Equine Vet Educ5(5), 262-266.
  • Woods J, Bergfelt D R & Ginther O J (1990)Effects of time of insemination relative to ovulation on pregnancy rate and embryonic-loss rate in mares. Equine Vet J22(6), 410-415PubMed.
  • Nequin L G, King S S, Matt K S & Jurak R C (1989)The influence of photoperiod on gonadotropin-releasing hormone stimulated luteinizing hormone release in the anestrus mare. Equine Vet J22(5), 56-358PubMed.
  • Shaw E B, Houpt K A & Holmes D F (1988)Body temperature and behavior of mares during the last two weeks of pregnancy. Equine Vet J20(3), 199-202PubMed.
  • Colquhoun K M, Eckersall P D, Renton J P & Douglas T A (1987)Control of breeding in the mare. Equine Vet J19(2), 138-142.
  • Michel T H, Rossdale P D & Cash R S G (1986)Efficacy of human chrorionic gonadotropin and gonadotropin releasing hormone for hastening ovulation in Thoroughbred mares. Equine Vet J18(6), 438-442.

Other sources of information

  • Horserace Betting Levy Board (2016)Codes of Practice.5th Floor, 21 Bloomsbury Street, London WC1B 3HF, UK. Tel: +44 (0)207 333 0043; Fax: +44 (0)207 333 0041; Email:enquiries@hblb.org.uk; Website:http://codes.hblb.org.uk.
  • McKinnon A O & Voss J L (1993) EdsEquine Reproduction.Lea & Febiger. pp 846-848. ISBN 0 8121 1427 2.
  • Ricketts S W (1992)Management/prognosis for the barren mareIn: Equine Stud Medicine & Artificial Insemination Course 3rd-7th Febuary 1992, Newmarket.British Equine Veterinary Association. pp 74-76.
  • Colahan P T et al(1991)Equine Medicine and Surgery.4th edn Vol 2. American Veterinary Publications, Inc. ISBN 0 939674 27 0. pp 994-1014. (Concise summary of main points.)
  • Allen W R (1987)Exogenous hormonal control of the mare's oestrus cycle. In: Proceedings of Ninth Bain Fallon Memorial Lectures, the Mare and Foal. August 6th-9th,1987, Sydney.Australian Equine Veterinary Association, 134-136 Hampden Road, Artarmon, 2064, NSW, Australia. pp 15-27.