Start teasing mares on day five or six after foaling, the Teagasc equine specialists recommend, and continue to tease mares in season daily through their heats so that the intensity of their signs can be monitored and to double check that the mare teases out as expected.
Mares that are believed to be gone out of season and/or in early pregnancy (less than 40 days) should still be teased at least two to three times a week so that short-cycling (early return to oestrus) mares and mares that lose their pregnancies and unexpectedly return to oestrus are not missed. Pay careful attention during the 16 to 18 days following ovulation to tease mares daily so as not to miss the beginning of the next oestrus period.
Mares that have been diagnosed as not pregnant but then fail to come back into season warrant a second ultrasound examination because it is possible that she was pregnant at the first scan but the embryo was missed because of its small size or because the mare conceived on a second, undetected ovulation a couple of days after the first.
Likewise, it can sometimes be difficult to accurately determine the early pregnancy status of mares that have cysts in the uterus. A pregnancy should grow and a cyst does not, otherwise they appear similar and there can be a difficulty in differentiating between the two in early pregnancy.
Mares that have been given prostaglandin (PG) to bring them back into heat also need close daily teasing so as not to miss the start of the next oestrus period. Late winter anoestrus and spring transitional mares should also be teased twice weekly to get a handle on their progress.
Some mares, such as maiden mares, performance mares and mares with very young foals simply do not display signs of behavioural oestrus even though they are cycling normally. In these instances, more intensive observation is required to detect subtle signs such as vulva lengthening, clear and slight mucous vulva discharge, increased restlessness, and vocalisations, all of which might indicate the mare is in season.
Timing of breeding
Breeding on the foal heat (six to ten days post-foaling) should only be considered if the mare has had a normal delivery, passed her placenta (the afterbirth) within four hours of delivery and experienced no other apparent problems.
Maiden and barren mares generally have a lower conception rate at the first heat of the season.
Mares are usually receptive to being bred for five to seven days. They normally ovulate during the last 24 to 48 hours of that heat period but accurately predicting exactly which day a mare will ovulate is impossible with teasing alone.
To maximise the chance of getting her in foal, the traditional natural breeding strategy is to cover a mare every 48 hours during her heat, beginning on the second day of showing oestrus signs.
This is continued until she is no longer receptive to the stallion. The average fertile stallion's semen will last for at least 48 hours in the mare.
However, the main disadvantages with this strategy are an increased risk of the mare developing a uterine infection and also the overuse of a busy stallion.
Semen is not sterile, and every natural covering introduces contaminants and bacteria as well as sperm into the uterus.
A healthy, young mare with good perineal conformation can clear contamination within 48 hours and this sort of mare is less likely to become infected as a result of breeding. However, the following categories of mares have a much more difficult time clearing contamination:
- Older mares which are predisposed to windsucking through poor perineal conformation.
- Mares predisposed to pooling of urine in the vagina.
- Mares that experience accumulation of uterine fluid.
- Mares that have a cervix that fails to relax completely during oestrus.
Another strategy is to breed the mare before, and as close to the time of ovulation as possible. This will limit the number of coverings/inseminations necessary, which is important for the infection-susceptible mares, busy stallions with large books of mares when the number of artificial insemination breeding doses is limited, and where frozen semen is used.
When the mare is bred 48 hours or less before her ovulation she should only need to be bred once during the cycle.
Table 2 shows the optimal times to cover or inseminate the mare, depending on the method of insemination.
In situations where breeding must be based solely on the mare's behaviour, one effective strategy -- for some farms with exceptionally good and careful teasing management -- is to breed mares on the third day of their behavioural oestrus and once more on the fifth day should they continue to tease strongly.
Experienced vets can accurately predict ovulation time. Using an ultrasound scanner, it is possible to be much more accurate in the timing of coverings relative to ovulation.
In general, when a dominant follicle reaches a diameter of 3.5 to 4cm and softens, it is a reasonable guesstimate to say that the mare is within 24 to 48 hours of ovulation.
This timing prediction can be tweaked based on how the follicle looks and feels, how strongly the mare is teasing in, what her uterine and cervical tone feel like, and previous ovulation histories. This is where record keeping is important.
Veterinary costs vs benefits
Deciding how much veterinary intervention is required in the breeding management of the mare is important.
While increased veterinary input increases costs in the form of professional fees and often materials such as hormones, washes/treatments, minimal veterinary input and scanning can bring its own hidden costs.
These are outlined by Teagasc as:
- Increased covering of the mare increases the chances of your mare being infected, increasing the possibility of her not conceiving and the subsequent necessity for more intense veterinary treatment, wash outs and injections.
- Less veterinary supervision may mean longer stays at stud or indeed missing ovulations, which proves costly through increased transport costs, and increased keep costs.
- Low veterinary input means that mares with reproductive problems are not identified quickly, thus wasting your investment.
- AI necessitates greater veterinary monitoring to ensure there is no wastage of semen.
Breeding decisions on how best to manage your mare will be influenced by your own individual circumstances so weigh up your options and follow the Teagasc advice to optimise your chances of getting your mare in foal first time.
The Teagasc equine specialist team of Norman Storey (051 644400), Wendy Conlon (091 845291), Declan McArdle (046 9026718) and Ruth Fennell (058 41211) are available with advice and support for all breeders.