Advice from our vets

There is much you can do to increase the chances of getting your mare in foal. Firstly, you should consider whether your mare is suitable for breeding. Please take advice from experienced professionals if you have questions that you would like to discuss. As a member of the breeders’ association,, you can get valuable advice and assistance in finding the appropriate stallion for your mare. Get in touch with the stud station to book a place for your horse and to discuss when, where and how the covering will take place.

You can also estimate the cost of the procedure. Choosing a stallion who is stabled at the station is least expensive. However, if you choose a stallion whose semen is transported within Sweden or from another country, the semen is usually shipped through the post or by air, which increases costs.

When you have made your decision, report your mare for insemination/covering via You will find the information required for registration in your horse’s passport. Be sure to bring along the passport when you arrive with your mare at the stud station. At the station your mare will meet other horses so you are advised to ensure that a parasite control has been preformed and that your mare is vaccinated against equine influenza and tetanus.

Importance of the mare
A mare´s health, fitness and body fat are important.  A healthy mare with normal to slightly above normal body fat, who is exercised moderately is usually easiest to get pregnant. Various medical conditions and medications can affect fertility. Pain and stress can also negatively affect the hormonal balance in the body. A balanced diet is of course very important, and nutritious green grass and light stimulate oestrus. If a mare still does not show signs of oestrus, contact with other horses, especially a stallion, can activate hormones and stimulate the libido.

A mare is at her most fertile between the age of 4 and 14 years. As the mare gets older, the fertility rate drops, but individual variations tend to be large. Mares who already have a foal by their side have a greater chance of falling pregnant even as they get older. Mares who competed for many years may find it harder to get pregnant, especially if they come directly from extensive training and active competition. Their bodies are more focused on physical achievement than reproduction.

Embryo transfer opportunity
If you have a very promising mare or a mare that is already performing well in competitions, showing that she has a good temperament and stamina, it is now possible to increase the chances of successful breeding via embryo transfer. The mare can then participate in breeding with the help a surrogate-mare who carries her offspring. Mares who experience trouble getting pregnant are not suitable for the process, while mares who easily become pregnant but do not manage to carry the foal to term are good candidates.

There are many factors that contribute to a successful embryo transfer. The process is time consuming and costly. For each donor-mare several recipient-mares are required, as oestrus and ovulation need to be synchronized with the donor-mare’s oestrus cycle, and her cycle may not always be predictable or regular. Registration of offspring produced by embryo transfer is now allowed within the Swedish Warmblood breed (SWB).

Greatest chance between May and July
Mares experience seasonal oestrus. In the transition between winter and spring the oestrus cycle is often long and many mares do not ovulate during this period. In late May and June when it is bright and warm oestrus is more marked and shorter, and the vast majority of mares ovulate regularly. This means that the mare is more likely to become pregnant during the period May to July, than say February to March. Mares who have foaled normally demonstrate oestrus approximately 6-10 days after foaling.

The oestrus cycle lasts on average about 20-21 days. Therefore, it may be advisable to visit the stud station approximately 15 days after the end of the mare’s last oestrus. For mares who have foaled a period of 7 or 25 days after foaling may be appropriate times to visit the stud station. This will allow for time to examine the mare and determine oestrus in order to optimise insemination/impregnation, which will in turn increase the chances for the mare to become pregnant.

The mare is examined at the collection centre
Before insemination, the mare is required to be healthy and must therefore be examined. A vet conducts a gynaecological examination of the mare’s genitals using palpation (feeling the ovaries and uterus by hand) and ultrasound. The mare is examined approximately every other day to determine the best time for insemination and to establish that ovulation has occurred.

It is important that you inform the stud station if your mare has previously showed signs of gynaecological problems, such as vaginal discharge, if the mare gone gall (not become pregnant the previous season), if she has thrown (spontaneous abortion) or shown signs of other illness. The vet then has the oppotunity to extend the first gynaecological examination with the collection of samples and to begin the appropriate treatment, for example of pyometra/uterine infection. Another very important reason for individual screening is to prevent the spread of infectious diseases.

Fresh or frozen semen?
Artificial insemination (AI), can be accomplished using fresh semen directly from a stallion stabled at the station, using transported chilled semen (TAI ) that is inseminated within 12-24 hours or using frozen semen (FAI). The highest success rate (i.e. pregnancy) is seen after insemination with fresh semen or natural service.
Insemination with frozen semen has the lowest conception rate and is best for mares with foals by their side or mares aged 4-8 years as they usually are more fertile.

If you choose a stallion whose sperm is available by transport within Sweden, the sperm is usually available 3-4 days per week. If you choose a foreign stallion timing for delivery varies and the station needs to plan in order to optimize insemination.

Stallion fertility is essential
A prerequisite for the mare to become pregnant is that the stallion’s fertility is good. Semen quality differs between individuals and transportation can affect sperm to varying degrees. This may mean that some stallions have good pregnancy rates with insemination using fresh semen at the station where the stallion is stabled, but considerably worse results if the semen is transported. If you are interested in this type of stallion, it is often best to take your mare to the stallion.

Find out more about more about the stallion/s you are considering using. Pregnancy and foal statistics from previous years are available in stallion calendars, breeding publications and through the Swedish breeding association’s website ( Stallions with good fertility have high conception rates per oestrus. As a mare owner is you customer – contact stallion owner/stallion holder if you have questions about fertility. If you have a mare who is hard to get pregnant or is a bit older, it is helpful to choose a stallion with very good fertility.

Best regards and welcome to Lövsta Stud Station,
Station Veterinarians Lena Malmgren and Görel Nyman