As horse enthusiasts, the dream of breeding a mare can be exciting, but for owners of older mares, a common question arises: “Is she too old to breed?” While age is a factor, understanding a mare’s reproductive health and history is crucial. This guide, drawing insights from veterinary expertise, explores the considerations for breeding older mares, ensuring a successful and informed breeding journey.
Understanding Mare Fertility and Age
Generally, a healthy filly, with proper nutrition, can be bred as early as two years old, though many experts recommend waiting until three. Mares can remain reproductively active into their late teens and even their mid-20s. However, it’s essential to recognize that fertility naturally declines with age. An older mare that has recently given birth has a better chance of conceiving again compared to a mare of similar age who has been barren. Even maiden mares, those who have never been bred, can be more challenging to get in foal as they age.
Assessing Reproductive Health: The Breeding Soundness Exam (BSE)
The most critical step in evaluating a mare’s breeding potential, regardless of age, is a thorough Breeding Soundness Exam (BSE) conducted by a veterinarian. This exam typically includes rectal palpation and ultrasound to assess the health of the uterus and monitor ovarian activity. As mares age, their estrus cycles can become less frequent or more irregular. The BSE helps detect follicles, cysts, and other ovarian structures, both normal and abnormal.
To gain further insight, especially with limited knowledge of a mare’s reproductive past, a uterine culture and biopsy are recommended. A uterine culture can identify subclinical infections that may hinder fertility, while a biopsy reveals microscopic details of the uterine lining (endometrium), identifying abnormalities not detectable through palpation.
A comprehensive evaluation also necessitates understanding the mare’s general medical and management history, alongside a detailed reproductive history.
General History should include:
- Age
- Purchase date
- Performance history
- Serologic tests
- Vaccination history
- Boarding facilities
- Diet (feed)
- Previous and intended use
- Medical and surgical history
- Past and present disease problems
- Weight fluctuations
Reproductive History (if available) should include:
- Age at first heat
- Heat dates and intervals
- Length of heats
- Age at first breeding
- Breeding dates
- Foaling dates and date of last foaling
- History of abnormal or assisted foalings
- Number of pregnancies and any abnormal pregnancies
- Previous year’s breeding cycle pattern
- Number of breedings required for conception
- Evidence of vaginal discharge
- Mothering ability and milk production
- Teasing and breeding methods employed (pasture, hand breeding, or artificial insemination)
Breeding Considerations for Older Mares
Peak fertility in horses is typically observed around 6 to 7 years of age. Fertility begins to decline around 15 years old, making conception more challenging and increasing the risk of pregnancy loss. A young, reproductively sound mare has a 50-60% chance of conceiving per estrous cycle when bred to a fertile stallion. In contrast, an older mare’s chance may be 30-40% or less. Consequently, older mares might require more estrous cycles to achieve pregnancy compared to younger mares.
It is advisable for a veterinarian to conduct a reproductive evaluation on an older mare before the breeding season commences. If the mare has no prior history of infertility, the exam might focus on ultrasound and a uterine culture. However, for mares with a history of infertility, the evaluation should be more extensive, including an assessment of perineal anatomy (vulvar angle and muscle tone), a vaginal speculum examination, digital examination of the cervix, uterine cytology and culture, an endometrial biopsy, and a thorough ultrasonographic evaluation of the reproductive tract.
Older mares may develop health issues that can negatively impact fertility. These can include poor perineal conformation, increased susceptibility to uterine infections, persistent post-mating inflammation, greater deposition of uterine scar tissue, endometrial cyst formation, a higher incidence of ovulation failure, and other contributing factors.
Conclusion: Informed Breeding for Mature Mares
Breeding an older mare requires careful consideration and a proactive approach to reproductive health. By understanding the natural decline in fertility with age and ensuring a comprehensive veterinary evaluation, owners can make informed decisions. The Breeding Soundness Exam, along with a detailed history, provides invaluable insights into the mare’s potential for successful conception and pregnancy. Consulting with an equine veterinarian is paramount to developing a tailored breeding plan for your mature mare.
