Artificial Insemination (AI) of horses
Mares can be bred naturally by the stallion (either at pasture or in a controlled environment with the stallion in hand) or by artificial insemination (AI). Natural service is very common but carries an increased risk to the mare, stallion and mare holders or the stallion handler. It is not uncommon for pasture bred horses to receive injuries and many of these may result in fertility or behavioural issues for the stallion. AI is breeding of a mare with semen that has been collected and then inseminated into the uterus or vagina using instruments or equipment rather than by natural service. AI has been around for years, in fact the earliest report that we have seen (Jim Bowen in the USA ) quotes an Arab chieftain in 1322 stealing some freshly deposited semen and breeding his own mare. Only the Thoroughbred breed actively campaigns against its use: why is still a mystery to those who understand reproduction. AI can be used to breed mares with fresh semen or the semen can be mixed with seminal extenders and thus treated with antibiotics and cooled for 24-48 hours or frozen for AI much later on.
What are the advantages of AI?
1) Disease control: This is accomplished by preventing skin contact such as in natural service. The most important diseases it protects against are transmission of the herpes virus- equine coital exthanema- and contagious equine metritis, which is caused by a bacteria. In addition antibiotics can be added to the semen at the time of insemination or collection and reduce or totally eliminate breeding the mare with any bacteria at all. The current outbreak of Equine Influenza (EI) may also be a good reason to consider AI in Thoroughbreds as we could effectively eliminate disease and maintain mare movement restrictions.
2) Decreases chances of injury: Semen is generally only collected every other day in an AI programme, so there is much less chance for injury. In addition semen can be collected on a phantom and a mare in heat may not even be needed. Not only does this almost eliminate injury to the mare (if she didn’t want to get served) and stallion but also it dramatically reduces the chances of injury to those staff involved in the breeding shed. It may be in future that farms could be in legal trouble when staff are hurt and AI could have been used.
3) Semen can be collected from stallions with problems: Each year stallions are either injured or have trouble breeding due to inherent libido (sexual behaviour) problems. Because semen only needs to be collected every other day it reduces the effects of breeding pressure and injuries.
4) Semen is evaluated each time it is collected: With natural service we are flying a bit blind because it is not until pregnancy rates are established can we assume that the semen was OK at the time of breeding. With AI we can look and measure parameters related to fertility every time we collect. One way to look at reproduction is to say that when we feel the testicles ‘we are feeling the future’ and when looking at semen we are ‘looking at history’, as one represents potential and the other the recent event of semen production.
5) Prevents stallion overuse:
A popular Thoroughbred stallion may be asked to breed as many as 4 mares in a
day. If he has a book of 200 then this would be expected to happen at least 10
times during the 100 days of the imposed breeding season. Mostly he is asked to
breed 2-3 times daily. If his fertility is good he can achieve around 97% of
mares in foal with good farm and veterinary management.
In an AI program the stallion could be collected three times per week and still have enough semen to breed the same numbers of mares (maybe more). Obviously this is less taxing for a stallion particularly if he has low libido.
6) Allows more mares to be bred: AI lets us divide the semen up into as many doses as he is capable of giving in an ejaculate. Typically that is around 10-15 doses on an every other day collection schedule. It is possible to bred more mares with AI but still difficult to achieve more than 400 pregnancies with even the most fertile horses in the defined breeding seasons (around 100 days). Thos who say AI has unfair advantages compared to natural service do not complain that a large book for natural service has been lifted to 200 mares from as little as 50, around 15 years ago and it is mostly to do with better education (much of which was learnt from AI and ET) and the use of more efficient drugs (ie Ovuplant). Veterinary and farm management have also improved dramatically.
7) Permits breeding of mares with problems: Each year mares are presented for natural service that may not be psychologically ready for service. Sometimes this is due to the mare’s own agitation and sometimes it may be because she has a ‘foal at foot’ and becomes worried about her foal (foal proud). In addition some mares may have physical disabilities that prevent her from being bred by natural service (such as laminitis)
8) Permits use of older valuable stallions: As stallions get older their sperm numbers decrease. This typically begins at around 13 years old. Many stallions are already exhibiting quite obvious sperm reduction by the time they are 16-17 and many are almost infertile by the time they are 19-20 years old. AI allows deposition of the correct number of sperm to be made for each mare and removes the guesswork.
9) Allows mares to be bred at the best time for conception: Because we can store semen either cooled or frozen mares can be bred when they are most suited for conception. In a natural service programme this would necessitate breeding the stallion as many as 5-6 times per day. Most stallions would not handle a breeding schedule like that for very long.
10) Increase pregnancy rates???? This is a fallacy. Although AI allows us the best opportunity to maximise fertility it is quite clear that management plays a huge part in farm fertility and if AI is improperly practised it can actually reduce pregnancy rates or even be an effective contraception. Have a look at our article on ‘Horse Breeding Efficiency’ on the web site.
What are the disadvantages of AI ???
1) Specialised equipment is needed: An artificial vagina (AV), thermometers, warmed containers and equipment, non-spermicidal gel and equipment to measure motility (warmed stage microscope) and sperm concentration are all necessary for AI to be practised properly. This is expensive and a well-equipped laboratory may cost in vicinity of $40,000 just for the equipment (without the building and fittings).
2) Technical expertise is needed: Personnel need to know how to make the AV so that it is right for the stallion and then how to collect and process the semen properly. Some stallions will not adapt very well to collection with an Artificial Vagina, especially if they are older and have had years of natural service.
3) Incorrectly practised AI can cause problems: Each year we consult on AI problems that are caused by management issues. You would be surprised to learn just how often the wrong lubricating gel is used in the AV and that there have been weeks before anyone realised that the pregnancy rates were disastrous.
How do we AI ?
collect semen: Build up an artificial vagina (AV) with hot water (around 550C
and leave it sit until the temperature is around 440C. Most stallions
like that temperature. Do not make it the AV hotter than 500C unless
you have a death wish (apart from hurting the stallions penis it may kill the
You can collect semen on a mare or a phantom. It is quite easy to train a stallion to breed a phantom.
Next get rid of the gel and measure the semen volume: The gel is removed using a filter and as it is ejaculated last it is quite easy to remove as long as you are quick. The semen volume is measured using a clean (preferably new) container that has been pre-warmed to 370C.
Then extend the semen: Semen extenders are usually milk based and protect the sperm against seminal plasma as well effects of ‘cold shock’. Semen in extender lasts longer and can be more easily examined to determine motility. It is imperative to extend semen if it is to be transported or a delay is anticipated from collection to insemination.
Measure the concentration: There are a variety of techniques to do this but we prefer the Animal Reproduction System Densimeter. This will cost around $7000 in Australia . It calculates the concentration by measuring the amount of light that is absorbed in a known diluted sample. It is very accurate and can be used to calculate the number of sperm and volume of semen needed to breed the mare with the right dose.
Have a look at the motility: Semen motility is measured as total and progressive. Progressive motility is a sperm that moves forward in a reasonably straight line and rotates its’ flat head as it swims. Motility must be examined with extended semen and using a heated stage microscope.
Calculate the dose of semen: Ideally about 500 X 106 progressively motile sperm (PMS) are needed to achieve consistent and maximum fertility. There are many stallions and many techniques that can be used to decrease this number but we strongly recommend starting with this number. Volume of raw semen = Insemination dose/(concentration X motility).
So if the insemination dose was 500 X 106 PMS and the concentration was 80 X 106 with a PMS of 50% the volume of raw semen would be 12.5 ml =500/(80 X .50).
Breed the mare: The raw semen is best added to extender early on after collection and the semen : extender ratio used to calculate the raw semen constituent so as the mare is bred with the right number of PMS. To breed the mare, she is first carefully cleaned and rinsed. Soaps and cleaning agents tend be spermicidal. The a gloved hand with a pipette is introduced into the vagina and the pipette passed gently through the cervix. The semen is then deposited into the uterine body.