Breeding an Old Horse
People often ask 'Is my mare too old to breed?' or 'How old can a stallion be and still breed?'. This article provides a response to these questions, with advice on how to minimise the risks associated with breeding an older horse.
Stallion
A stallion can breed into his 20s and there are a number of cases of breeding into their 30s. Provided that the mating is supervised correctly and the stallion is in good health (not feeble), an older stallion can be used for stud services. From the late teens onwards, the amount of semen produced by the stallion gradually declines. Likewise, the strength of the semen overall declines as well. The result of this is that the older stallion is progressively less likely to make a mare pregnant in a single mating. However, there is no age at which one can say that a stallion can no longer make a mare pregnant. If you wish to check the reproductive capability of your stallion, a veterinarian can take a semen sample (using a dummy) which can then be sent to a laboratory to examine the quantity and quality of semen.
Although the quality and quantity of the semen declines with age, the genetic material (genes) within the semen is unaffected. Consequently, the quality of a foal produced by a stallion is the same regardless of the age of the stallion. It is only the probability of the mating resulting in a pregancy which is age related. There is some statistical research showing a potential decline in genetic quality with age, but this difference is so tiny (especially when compared to major factors, such as stallion and mare quality) that it can be ignored for practical purposes.
Breeding is typically done using a dummy (to collect semen for artifical insimination) or by placing a mare in a station or by natural breeding in the field. The first method is of course quite safe unless the stallion has become feeble. The second method is also acceptable as long as the stallion is in good health and does not have any medical conditions which would affect this (e.g. arthritis, weak heart, muscle wastage). However, caution should be used with the third method due to the risk of physical strain or injury. Field mating has a number of risks even for a young stallion and some of these risks are increased for the older stallion:
- Older stallions may be slower and less agile, so are less able to avoid bites or kicks by mares.
- Older stallions can be injured more easily and are slower to recover from injuries
- Mares often make stallions 'work' by requiring that the stallions chase them. When faced with a much younger and faster mare, a stallion can over exert itself to the point of serious self injury (e.g. permanent damage to the lungs).
Consequently, while field mating always requires close supervision, it needs to be monitored even closer with an old stallion, particularly if faced with a reluctant mare. In some cases, one may decide that the stallions age and health make field mating inadvisable.
Mares
Mares have been bred succesfully into their 20s and even their 30s, giving birth to healthy foals without any apparent health problems for either mare and foal. However, from the teens onwards, the ability of a mare to conceive decreases, while the risk of health issues to both mare and foal (including terminated pregnancy or birthing a dead foal) increase. Consequently, one needs to consider carefully the risks when breeding with an older mare:
- Will the mare conceive? If it is likely that she should not, before paying a stud fee try to ensure that the contract provides a refund (not a second try) if the breeding does not result in a live foal.
- Will the foal be carried to term and be born healthy? One can never be certain, but with older mares problems are more likely. See above note on the stud contract.
- Will the mare be affected? Prior to mating a mare, both her general health and the health of her reproductive system should be checked by a veterinarian, preferably one that specialises in horses.
The maximum age for breeding a mare depends mainly on the individual mare. A horse which has received good nutrition, has been well cared for all of its live, and has not been over-worked can be bred much later than a mare which has not had these benefits. Also, a mare which has foaled before can generally be bred at an older age than a maiden.
Long-lived breeds (e.g. ponies, Arabians) mature and age slower than short-lived breeds. Consequently, mares from long-lived breeds can be safely bred to a later age.
Aside from the general health of the mare, there are a number of specific areas which can be examined to determine her breeding capability:
- Uterus - Scars or Fibers. The uterous of a mare can be damaged by previous pregancies, resulting in scar tissue or fibrosis. However, even a maiden mare can show fibrosis as early as her teens due to aging. This can may it more difficult for the mare to conceive. It may also interfer with the development of the fetus, resulting in a smaller and weaker foal.
- Uterus - Endometritis. Endometritis is inflamation of the uterus and occurs naturally after mating due to the introduction of bacteria and other foreign matter. Normally it clears within a day of mating, but in older mares it may take longer, which may prevent pregancy.
- Uterus - Cysts. Cysts become more common as the horse ages and can prevent pregnancy. In some cases, they can be removed surgically or by laser treatment.
- Cervix. The cervix, like the uterus, can be worn as a result of previous pregancies or as a result of age.
- Vagina. - The vagina by be damaged, sunken or tipped back. These conditions can interfer not only with birth, but also can increase the risk of infection and thereby the risk of a terminated pregnancy.
- Ovum - The eggs of the mare tend to become weaker with age, reducing the chances of conception and increasing the risk or early termination of the pregancy.
- Organs. Pregnancy puts a strain on internal organs, so even an apparently healthy horse can develop problems as her system is put under increased strain by the pregnancy. In addition to observing the general health, analysis of a blood sample to check the function of internal organs can be useful.
There are a number of tests available to check the health of the reproductive system (uterus, cervix, vagina), including: visual examination, palpation to feel for abnormalities, ultra-sound, internal camera, biopsy of uterus (taking a tissue sample for laboratory analysis), swabs to take bacteria sample and check for infection. Some veterinarians offer 'Breeding Soundness Examination', otherwise known as a BSE, which use a combination of these techniques to examine the reproductive organs. However, while such examinations may identify problems which can prevent a successful pregancy and may suggest treatments to improve the chances of success, no examination can provide a 100% guarantee that the mare will conceive or have a healthy foal.
