IT is thought that artificial insemination (AI) first began with the Arabs many years BC, but the first recorded incident was in 1322, when an Arab sheikh stole semen from a rival’s stallion!

It wasn’t until 1902 in Denmark that it was promulgated that AI could be used for breed improvement. At this time, the USA and Britain were slower to adopt AI practices than their continental counterparts and instead followed the lead of thoroughbred breeders of the day. The real push to develop AI in the horse came from the Russian Royal Stud in 1909, but the thoroughbred studbook has yet to adopt AI in its own breeding practices.

Nowadays, mare owners can chose a stallion who stands anywhere in the world, or even a stallion who is dead for several years, and breed their mare with that stallion in their own country, or sometimes even county. Artificial insemination has made this a reality and the uptake of AI services is growing rapidly within Ireland within the sport horse industry.

On the continent, some studbooks report that up to 100% of breedings occur via AI. There are many ways in which stallion semen can be processed and there is no single method that suits every stallion best. When a stallion is collected for AI, his semen can ultimately follow one of three routes; fresh, chilled or frozen semen processing. In all cases, the semen should be mixed with a suitable extender which serves to protect the sperm.

Chilled Semen

The stallion is collected with the use of a breeding dummy, usually, and an artificial vagina (AV). The collected semen is carefully handled to avoid damage to the fragile sperm and a number of characteristics are assessed in the laboratory. The insemination dose is based on the principle that mares should be typically inseminated with between 250 and 500 million progressively motile sperm (PMS).

The PMS are the sperm likely and capable of fertilising the mares’ eggs and ultimately result in pregnancy. Not all stallion semen has the same concentration and so not all volumes of semen per recommended dose are the same. Typically a chilled semen insemination dose is 10-25mls, but this can vary.

Chilled semen is best stored at five degrees Celsius at all times and should be deposited into the mare within 12-36 hours after collection. This allows enough time for semen to be collected and delivered to the mare within Europe within a suitable timeframe for success.

Advantages

  • Less expensive to ship semen than ship your mare
  • Less expensive (in some cases) to ship than frozen semen
  • Mare/foal stress and risk is minimised as she can be inseminated close to home
  • Mare/foal livery costs can be minimised
  • Greatly increases stallion choice
  • Next day delivery is available midweek from most EU countries into Ireland.

    • Disadvantages

  • Not all stallions are available with chilled semen
  • Health papers and shipping costs are incurred with imported semen (health papers are always required for any semen movement between different countries)
  • Chilled semen is not available seven days a week due to courier limitations. Deliveries from the continent into Ireland are Tuesday to Friday only.Chilled semen deliveries are affected by bank holidays across Europe.

    • Frozen Semen

    Stallions are collected in the same way as described above for the production of frozen semen, although they will typically be collected outside of the breeding season when the semen is more suited to the freezing process. The semen undergoes laboratory assessments and processes and is ultimately frozen in liquid nitrogen (-196 degrees Celsius) in 0.5ml straws (or less often in 5ml macro straws).

    Frozen semen, when handled and maintained correctly, can remain viable for years and so it is in this way that we can produce foals from stallions even after their demise. There is great variability in the quality of frozen stallion semen and this is down to, not only the production and handling of the semen in the first instance, but individual stallion variation also.

    Although the number of progressively motile sperm is not a guarantee of conception, it is one of the most commonly quoted indicators of semen performance outside of the pregnancy rate. In the case of frozen semen, the ‘post thaw’ progressive motility is the parameter considered and the most common minimum standard is > 35% PMS.

    Frozen semen with a post thaw progressive motile sperm percentage of 40 or higher is considered to be good. Similar to chilled semen, an insemination dose exceeding 250 million PMS post thaw are likely to optimize fertility. Low dose insemination techniques allow for fewer sperm to be used but these techniques are not suited to all stallions’ semen.

    There is a common belief that chilled semen has a higher fertility than frozen-thawed semen (omitting individual stallion variation), however there are very few studies in this area. There are several studies which clearly show that seasonal and per cycle pregnancy rates are comparable between chilled and frozen semen. However, individual stallion and mare variation must always be considered in order to achieve the best possible outcome.

    Advantages

  • Semen can be organised in advance and stored at your veterinary practice ready for use
  • Semen from competing and deceased stallions can be made available
  • Semen can be purchased outright and stored for use at any time in the future
  • There is less emphasis on mare cycle manipulation to achieve a mid-week insemination, which can increase the pregnancy rate
  • Greatly increases stallion choice as stallions from anywhere in the world may be accessible
  • If your mare’s cycle is abnormal and the veterinary surgeon decides not to inseminate, you can keep the frozen semen for the next cycle.

    • Disadvantages

  • Not all stallions are available with frozen semen and not all stallions have good quality frozen semen
  • Health papers and shipping costs are incurred with imported semen (health papers are always required for any semen movement between different countries)
  • Frozen semen deliveries in some instances are more expensive due to specialised shipping equipment required
  • Fewer veterinary surgeons are experienced in the use of frozen semen and more ultrasound scans are required
  • Poor handling of the frozen semen can greatly affect the quality of the semen and therefore pregnancy rates
  • Not all mares are suitable for frozen semen.

    • Emma-Rose Conroy is a veterinary surgeon and the owner of Euro Stallions (Ireland) Ltd. Euro Stallions is an EU-approved semen storage centre and stallion semen agency, based in Co Offaly, that represents many of the very best stallions from around the world as well as many up and coming youngsters. Further information can be found at www.eurostallions.ie