Recommendations prior to breeding
To maximise the fertility of your breeding programme we recommend the following:
Mare age: Older mares, greater than 14yo have reduced fertility. These mares are more prone to endometritis (infection of the uterus) and uterine cysts. It is worth nothing that fertility decreases exponentially with age and not in a linear fashion.
Mare foaling status: Mares with a foal at foot and young maidens (3 – 10yo) are usually the most fertile group of mares. “A pregnant uterus is a healthy uterus” so we do not usually recommend resting mares to optimise fertility.
Semen quality: There is huge variability between stallions in their fertility after artificial insemination so it is best to use semen from stallions with a record of good fertility. It is important that mares are inseminated with high numbers (>300million) motile sperm and that the semen is handled carefully by experienced personnel.
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Bringing you mare into oestrus
Non pregnant mares: For ease of timing we recommend that mares known to be in mid to late cycle are injected with Prostaglandin (PG) on a thursday or friday with an aim to start scanning the following Monday.
Mares with foal at foot: Once your mare has foaled she should be checked 9 days later to make sure her uterus is clean and returning to its normal size. We do not normally recommend using a foal heat to breed from unless it is late in the season or your mare is young and has a very clean uterus.Our usual routine is to allow a normal foal heat and then inject the mare around 7-10 days later with prostaglandin / PG (Preferably on a thurs or a friday). Following this injection we will start scanning her the following Monday
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Fertility expectations
Natural mating: In Thoroughbreds, 50 - 60% of mares conceive per cycle. Around 89% of mares are pregnant by the end of the season and of those around 79% of mares will go on to produce a live foal.
AI with Fresh / chilled semen: When fresh or good quality chilled semen is used for artificial insemination (AI) there are slightly higher (5 – 10%) pregnancy rates per cycle compared with natural mating. An healthy fertile mare will take 1 – 2 cycles to conceive.
Frozen semen: There is much greater variability between stallions with frozen semen so for an accurate expectation of fertility an examination of the particular stallions breeding record (number of mare cycles per pregnancy) is required.
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Ultrasound Scanning Timeline
Natural mating: Tracking your mares cycle through ultrasound examinations we can determine the optimum time to take her to the stallion for natural mating. In these situations it is ideal if we evaluate your mare after mating as well to rule out any problems with uterine infection or ovulation.
Fresh / chilled semen AI: The management of the mare’s oestrous cycle for artificial insemination is similar to that for natural mating. Typically there are 4-10 ultrasound scans per oestrous cycle to optimise the timing for ordering the semen, inseminating the mare and to rule out post breeding infections. Mares are scanned every 24-48 hours until they have a follicle deemed big enough to be induced to ovulate. 24 hours post injection insemination is performed. The majority of mares will ovulate within 24-48 hours post injection. Optimum pregnancy rates occur when insemination occurs in a 30 hour window around ovulation. (24 hours pre-ovulation and 6 hours post-ovulation) Post ovulation scans are performed 24 hours after insemination to confirm ovulation and check for any post breeding uterine infection / fluid build up.
Frozen semen: Scanning of mares for insemination with frozen semen is identical to that of chilled semen up to the point of the injection to induce ovulation. 24 hours post injection mares are scanned every 4-6 hours with the aim to inseminate at / or as close as possible to the point of ovulation. Typically this is at the 36 or 42 hour scan post injection. With good frozen semen optimum pregnancy rates occur within an 18 hour window around ovulation. (12 hours pre-ovulation and 6 hours post-ovulation). As the volume of semen is much less when using frozen semen we perform deep inter-uterine insemination. This is where the semen is deposited at the tip of the uterine horn as close as possible to the ovulating ovary to maximise pregnancy rates. Post-ovulation and pregnancy scans are performed as per fresh/chilled semen.
Pregnancy diagnosis: It is very important that mares are scanned by ultrasound at 15-16 days after ovulation to ensure that they are pregnant and to rule out twins. If twins are diagnosed at an early stage they can be treated successfully in most cases. Most pregnancy loss occurs between 20 and 30 days so we also recommend that a pregnancy scan be performed every 10 days until a mare is 45 days pregnant. Typically mares are scanned on day 16,25,35 and 45. By scanning at day 15-16 if the mare is not pregnany she can be scanned up again for another insemination without missing a cycle.
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