ISSN 2398-2977      

Reproduction: management - female



  • 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 most breeds undergo a period of seasonal acyclicity (seasonal anestrus) during the winter months.
    • Brood mares are not selected on the basis of reproductive performance, but rather on the athletic performance of themselves and their offspring.
    • Management failure to detect estrus and determine optimal time for breeding.
    • Poor semen quality.
    • Management 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, ie determining whether a mare is sexually receptive by exposing her to a stallion or gelding, is a commonly used technique in most 'natural cover' and some artificial insemination programs. 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 in 'natural cover' systems, ie where a stallion is breeding the mare. May also be used by some studs where artificial insemination is practiced Reproduction: artificial insemination.
  • Keen, sensible teaser stallion (or gelding).
  • 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

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 (clitoral 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:
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 from PubMed and VetMedResource.
  • Roser J F & Meyers-Brown G (2019) Enhancing fertility in mares: recombinant equine gonadotrophins. J Equine Vet Sci 76, 6-13 PubMed.
  • Finan S A, Lamkin E L & McKinnon A O (2016) Comparative efficacy of BioRelease Deslorelin® injection for induction of ovulation in oestrus mares: a field study. Aust Vet J 94 (9), 338-340 PubMed.
  • Henderson I S, Brama P, Osborne M & Beltman M E (2012) Interovulatory intervals in mares receiving deslorelin implants in Ireland (2009 to 2010). Vet Rec 170 (21), 541 PubMed.
  • Squires E L (2008) Hormonal manipulation of the mare: A review. J Equine Vet Sci 28 (11), 627-634 SciDirect.
  • MacPherson M & Blanchard T L (2005) Breeding mares on foal heat. Equine Vet Educ 17 (1), 44-52 WileyOnline.
  • Meyers P J (1993) Methods of controlling and synchronizing oestrus in the mare. Equine Vet Educ 5 (5), 262-266 WileyOnline.
  • 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 J 22 (6), 410-415 PubMed.
  • 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 J 22 (5), 56-358 PubMed.
  • 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 J 20 (3), 199-202 PubMed.
  • Colquhoun K M, Eckersall P D, Renton J P & Douglas T A (1987) Control of breeding in the mare. Equine Vet J 19 (2), 138-142.
  • Michel T H, Rossdale P D & Cash R S G (1986) Efficacy of human chorionic gonadotropin and gonadotropin releasing hormone for hastening ovulation in Thoroughbred mares. Equine Vet J 18 (6), 438-442.

Other sources of information

  • Horserace Betting Levy Board (2019) 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:; Website:
  • McKinnon A O & Voss J L (1993) Eds Equine Reproduction. Lea & Febiger, USA. pp 846-848. ISBN: 0812114272.
  • Ricketts S W (1992) Management/Prognosis for the Barren Mare. In: Equine Stud Medicine & Artificial Insemination Course 3rd-7th Febuary 1992, Newmarket. British Equine Veterinary Association, UK. pp 74-76.
  • Colahan P T et al (1991) Equine Medicine and Surgery. 4th edn Vol 2. American Veterinary Publications Inc, USA. ISBN: 0939674270. pp 994-1014.
  • Allen W R (1987) Exogenous hormonal control of the mare's oestrus cycle. In: Proc 9th Bain Fallon Memorial Lectures, the Mare and Foal. Australian Equine Veterinary Association, Australia. pp 15-27.

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