Introduction

• Horses are classically described as being ‘long day seasonal breeders’. Most mares are acyclical, ie the reproductive tract is inactive, during short days (the winter, non-breeding season), and cycle regularly during long days (the summer, breeding season).
• In between periods of cyclicity and acyclicity (in spring and autumn), mares experience two ‘transitional’ periods, during which they may cycle erratically.
• The timing of assessment of fertility depends upon the reason for carrying out the examination.

Uses

• Assessment of the likelihood of a mare becoming pregnant to a fertile stallion (including natural mating, fresh, chilled, and frozen semen) inseminated at an appropriate time in the estrous cycle; AND maintaining the pregnancy to term resulting in a viable foal. In this scenario, the examination would most usually be carried out during the breeding (long days) season.
• Assessment of a mare who has failed to conceive as a result of covering or insemination:
  • These examinations may be carried out during the breeding season, at the end of the breeding season, or during the non-breeding (short days) season.
  • Carrying out a breeding soundness examination at the end of the breeding season or during the non-breeding season has the advantage that there is a prolonged period of sexual rest and acyclicity, in which mares can be treated (particularly useful for intrauterine treatments).
  • The disadvantage is that it is impossible to assess during the non-breeding season whether the mare cycles regularly during the breeding season.

Advantages

• Assessing the suitability of a mare for reproductive purposes: a maiden mare, a mare for sale.
• Diagnosis of the reasons for a mare not being pregnant, despite appropriate breeding management, to facilitate treatment.

Disadvantages

• The process can be time consuming and expensive.
• The predictability suggests a likelihood of suitability as a broodmare, or of a mare becoming pregnant following treatment, rather than being definitive.

Requirements

Preparation

Procedure

Aftercare

Outcomes

Prognosis

• Depends on the findings.

Further Reading

Publications

Refereed papers

• Recent references from PubMed and VetMedResource.
• Gunn A J, Chopin J B & Norman S T (2012) Examination of the mare for reproductive purposes. Aust Equine Vet 31 (4), 37-42 SciQuest.
• Snider T A, Sepoy C & Holyoak G R (2011) Equine endometrial biopsy reviewed: Observation, interpretation, and application of histopathologic data. Theriogenology 75 (9), 1567-1581 PubMed.
• Kenney R M (1978) Cyclic and pathologic changes of the mare endometrium as detected by biopsy, with a note on early embryonic death. JAVMA 172 (3), 241-262 PubMed.

Other sources of information

• Brinsko S et al (2011) Breeding Soundness of the Mare. In: Manual of Equine Reproduction. Eds: Brinsko S et al. 3rd edn. Elsevier. pp 30-53.
• Bowman T R J (2011) Direct Rectal Palpation. In: Equine Reproduction. Eds: McKinnon A O, Squires E L, Vaala W E & Varner D D. Wiley, UK. pp 1904-1913.
• Card C E (2011) Endoscopic Examination. In:  Equine Reproduction. Eds: McKinnon A O, Squires E L, Vaala W E & Varner D D. Wiley, UK. pp 1940-1950.
• Lear T L & Villagomez D A F (2011) Cytogenetic Evaluation of Mares and Foals. In: Equine Reproduction. Eds: McKinnon A O, Squires E L, Vaala W E & Varner D D. Wiley, UK. pp 1951-1962.
• LeBlanc M M (2011) Uterine Cytology. In: Equine Reproduction. Eds: McKinnon A O, Squires E L, Vaala W E & Varner D D. Wiley, UK. pp 1922-1928.
• Love C C (2011) Endometrial Biopsy. In: Equine Reproduction. Eds: McKinnon A O, Squires E L, Vaala W E & Varner D D. Wiley, UK. pp 1929-1939.
• Pycock J F (2011) Ultrasonography. In: Equine Reproduction. Eds: McKinnon A O, Squires E L, Vaala W E & Varner D D. Wiley, UK. pp 1914-1921.
• Ricketts S W (2011) Uterine and Clitoral Cultures. In: Equine Reproduction. Eds: McKinnon A O, Squires E L, Vaala W E & Varner D D. Wiley, UK. pp 1963-1978.
• Zent W W (2011) History. In: Equine Reproduction. Eds: McKinnon A O, Squires E L, Vaala W E & Varner D D. Wiley, UK. pp 1897-1899.
• Zent W W & Steiner J V (2011) Vaginal Examination. In: Equine Reproduction. Eds: McKinnon A O, Squires E L, Vaala W E & Varner D D. Wiley, UK. pp 1900-1903.
• Kannegieter N & Major D A (2004) Guide to Examination of Horses. Equine Vet Aus pp 124-127.
• Pycock J (1998) Evaluation of the Reproductive System in Stallions and Mares for Breeding Purposes. In: British Equine Veterinary Association Manual. Eds: Mair T. BEVA, UK. pp 138-147.

Organisation(s)

• Horserace Betting Levy Board (online) Codes of Practice. London, UK. Website: www.codes.hblb.org.uk