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Artificial insemination (AI) has been used regularly in horse breeding since the beginning of the 20th century. There are some restrictions on the use of AI, most notably from the General Stud Book, which regulates the thoroughbred.

AI involves two key processes:

  • The collection, evaluation and dilution of semen from the stallion
  • The well-timed infusion of sperm into the mare’s uterus

Sperm must be thoroughly examined to make sure that it is of sufficient quality to be used in an AI programme. It must also be processed properly to ensure that it retains its fertilising potential.

AI in the horse is technically difficult and not cheap. Many mare owners expect the costs to be less for AI since the mare does not have to go to stud – but there can be considerable costs involved.

The overall pregnancy rates at the end of the season vary between 50% and 90%, with an average of around 75%-80%. Some mares lose the pregnancy and the live foal rate is around 70%.

Pros and cons of artificial insemination

Advantages include:

  • Eliminates cost and stress of transporting a mare and perhaps her foal
  • Greater number of mares can be inseminated
  • An increased choice of stallions, particularly from abroad
  • The mare’s owner can retain control over the management of the mare and foal
  • Regular semen evaluation
  • Extenders with proper antibiotics helps preserve the longevity of sperm and minimises bacterial contamination
  • AI reduces the risk of sexually transmissible diseases spreading throughout a breeding population or between farms, as long as the correct procedures are followed.

Disadvantages include:

  • Higher costs
  • Strict regulations to prevent the control of diseases
  • Need for adequate infrastructure in order to transport the semen
  • Semen from some stallions will not tolerate the cooling and/or the freezing and thawing process
  • Lack of appropriately trained and skilled vets

The role of the vet in equine AI is crucial, although appropriately trained “AI technicians” can perform the insemination of the mare only a vet can perform the necessary checks to ensure the mare is ready.

Frozen semen

Advantages include:

  • Semen can be transported easily internationally
  • Semen can be used from competing or injured stallions
  • Semen from potentially valuable stallions can be frozen and stored indefinitely

Disadvantages include:

  • Pregnancy rates are often disappointing
  • Charges for freezing stallion spermatozoa are relatively high
  • Thawed frozen semen has a short life span
  • Frequent veterinary examinations are necessary

Breeding assessment for mares

Mares should have a thorough pre-breeding assessment before breeding via AI, this should include a complete breeding history of the mare for the past five years and the following should be considered:

  • Age: fertility declines once a mare is over 10 years old
  • Previous breeding history

Accurate prediction of ovulation is important because the best time for AI with chilled semen is in the 24hr leading up to ovulation. Pregnancy rates will generally fall if insemination is outside this range. This time interval is shorter than if fresh semen or natural mating is used, and the window of opportunity is even shorter with frozen semen.

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