In Thoroughbreds, 50 - 60% of mares conceive in each oestrous cycle after natural mating and by the end of the breeding season 89% of mares are pregnant. However only 79% of mares go on to produce a live foal.

When fresh or good quality chilled semen is used for artificial insemination (AI) we expect slightly higher per cycle pregnancy rates compared with natural mating. It normally takes 1 – 2 cycles for a fertile mare to conceive.

The fertility of frozen semen ranges from 0 – 70% per cycle due to the variability of the “freezability” of different stallions. Internationally, the reported pregnancy rates are around 40% per cycle. It normally takes 2 – 3 cycles for a fertile mare to conceive.


Breed from young mares! Older mares, greater than 14yo have reduced fertility. These mares are more prone to uterine infections and cysts. Generally, either fresh or chilled semen works better than frozen semen in these mares.

A pregnant uterus is a healthy uterus! Mares with a foal at foot and young maidens (3 – 10yo) are usually the most fertile group of mares. Barren mares usually benefit from insemination with fresh or chilled semen and save your frozen semen for when she has a foal at foot.

Use good quality semen: Do your homework! We can obtain semen from almost anywhere in the world if you can provide us with contact details for the stud. Make sure you buy a dose of more than 300million motile sperm and that the semen is handled by professionals.


Non pregnant mares: Ask your regular vet to treat your mare with an injection of prostaglandin (PG) and then organise to deliver your mare to EquiBreed 3 days later. Or we can do it for you as part of your programme.

Foaling mares: Once your mare has foaled then she should be checked 9 days later by your regular vet to make sure her uterus is healthy. Normally we do not recommend using artificial insemination in mares during foal heat. An easy protocol is to organise to treat the mare with a PG injection on day 21 after foaling. Three days after her injection she can be brought to EquiBreed for breeding management.


Natural mating: We can manage your mare’s breeding programme and “walk her in” to the stallion for natural mating. We also manage her after breeding to confirm ovulation and minimise the risk of infection.

AI your mare with fresh, chilled or shipped semen: The management of the mare for AI is similar to that for natural mating. We examine your mare multiple times to get the timing right for ordering the semen, AI and to treat post breeding infections.

AI your mare with frozen semen: Frozen semen only survives for about 6h after thawing. We aim to inseminate your mare with frozen semen within 2-4h of ovulation. So we scan your mares all day and night for you!

AI your mare with epididymal sperm: If you have produced an amazing colt and would like to breed from him and geld him….we can freeze his epididymal sperm at the time of gelding and then inseminate your mares with frozen epididymal sperm.

Sex sorted semen: This is now available in New Zealand as a result of a collaboration between Sexing Technologies and EquiBreed NZ. If you would like to choose the sex of your foal at the time of insemination then please contact us.

All semen used for AI at EquiBreed NZ is evaluated and recorded by our computerised AndroVision®semen analysis system to allow objective semen quality evaluation.