If you’ve ever wondered what it means for a female horse to be ‘fixed’ or wondered about the pros and cons of spaying a mare, you’ve come to the right place. In this comprehensive guide, we’ll cover everything you need to know about fixed female horses.

If you’re short on time, here’s the key thing to know: getting a female horse spayed (known as ‘fixing’, ‘neutering’ or ‘ovariectomy’) involves surgically removing her ovaries and uterus. This prevents her from coming into heat, getting pregnant and giving birth.

It’s typically done for population control, health or behavioral reasons.

What Does ‘Fixed’ Mean for a Female Horse?

Definition of a Fixed Female Horse

Fixing a female horse refers to the surgical procedure known as an ovariectomy or spaying, which involves removing the mare’s ovaries and uterus. This leaves the mare unable to reproduce and eliminates her heat cycles. Some key things to know about fixing a female horse:

The mare’s ovaries and uterus are completely removed. This differs from a hysterectomy in humans, where only the uterus is removed. With an ovariectomy, the ovaries are also taken out.It eliminates the ability to reproduce. A fixed mare can no longer become pregnant and give birth. The heat cycles also stop permanently.It’s typically done through flank surgery. The vet makes an incision in the flank area and removes the organs through that opening. It’s a more invasive surgery than neutering a male horse.

Other Names for the Procedure

Some other terms used to refer to fixing a female horse include:

  • Spaying – This is the most common alternate name
  • Ovariectomy
  • Ovary removal
  • Sterilization
  • So you may hear people refer to getting a mare “spayed” rather than “fixed”, but both terms refer to the surgical procedure that removes the ovaries and uterus.

    Reasons for Fixing a Mare

    Why might a horse owner choose to have this procedure done on their female horse? Here are some top reasons:

  • To eliminate heat cycles – This allows the mare to focus her energy and nutrients on other activities rather than reproduction. It also makes them easier to manage.
  • To decrease reproductive system problems – Fixing prevents ovarian, uterine, and mammary tumors which mares are prone to as they age. It may also help prevent reproductive tract infections.
  • To change unwanted behaviors – Some mares exhibit more defiant or difficult behaviors when in heat.
  • For convenience – Owners may not want to deal with breeding their mare.
  • For medical reasons – Such as ovarian cysts or infections that are difficult to treat otherwise.
  • Of course, the mare’s age, health status, and intended use will factor into the owner’s decision as well. But in general, fixing can improve manegeability and prevent health issues in mares not meant for breeding.

    The Spay Procedure for Mares

    Pre-Op Preparation and Exams

    Before a spay procedure can take place, the veterinarian will conduct a full physical examination of the mare to ensure she is healthy enough for surgery. A blood panel, urinalysis, and possibly x-rays or an ultrasound may be recommended. The mare’s reproductive history will also be reviewed.

    She should be current on all vaccines and deworming prior to surgery.

    The evening before surgery, food is withheld to prevent complications from vomiting under anesthesia. However, the mare has unlimited access to water until being admitted to the clinic on surgery day. Upon admission, an IV catheter is placed and antibiotics and pain management medication is administered.

    Different Surgical Methods Used

    There are a few surgical methods veterinarians may use to spay a mare:

    • Flank approach – This involves two incisions in the mare’s flank area to access the ovaries, which are then removed.
    • Ventral midline approach – One long incision is made from the mare’s udder to her sternum allowing access to remove both ovaries.
    • Laparoscopic surgery – Tiny incisions are used to insert a camera and instruments to visualize and remove the ovaries.

    The surgery typically lasts from 30 minutes to one hour depending on the technique. Veterinarians will choose the approach based on their expertise and the individual mare’s needs.

    Aftercare and Recovery Time

    Most mares only need to stay overnight at the veterinary clinic post-surgery. An Elizabethan collar, pain medication, and antibiotics are sent home to aid in a smooth recovery. The incision site(s) should be monitored for signs of infection and the mare should be confined and restricted from running/playing for 7-10 days.

    Exercise can gradually be increased after 2 weeks. Complete healing of the abdominal incisions takes approximately 6 weeks. At this time, the mare can resume normal activity. According to the American Association of Equine Practitioners, the long-term complication rate associated with elective ovariectomy is low at approximately 2%.

    Most mares adjust extremely well to life without ovaries and heat cycles.

    The Pros and Cons of Spaying Mares

    Potential Health Benefits

    Spaying, or ovariectomy, can provide several potential health benefits for mares. Here are some of the main advantages:

    • Eliminates the risk of ovarian tumors – Mares have a relatively high rate of ovarian tumors. Spaying removes this risk entirely.
    • Reduces risk of uterine infections – Older mares who are not bred are prone to uterine infections. Spaying prevents this problem.
    • No heat cycles – Spayed mares do not come into heat, which can make them easier to manage.
    • Prevents pregnancy – Spaying guarantees mares cannot accidentally become pregnant if exposed to stallions.

    According to a 2000 study, spaying was shown to significantly increase life expectancy in mares. So there are compelling health reasons to consider this procedure in many cases.

    Drawbacks and Risk Factors

    However, there are also some potential drawbacks and risks to be aware of with spaying mares:

    • Surgical procedure risks – Like any surgery, there are inherent risks with anesthesia and complications. Infection, bleeding, and slow healing are possible.
    • Loss of hormones – The ovaries produce hormones that affect mares’ metabolism and behavior. Spayed mares may be at greater risk of laminitis.
    • Personality changes – Some mares become more docile and easy going after being spayed. But a few may become more irritable and aggressive.
    • Coat changes – The coat may become thicker and shed out differently in spayed mares.
    • Requires aftercare – Spaying requires several weeks of stall rest during recovery. Owners need to provide proper aftercare.

    According to the Kentucky Equine Research, mares older than 10 years are better candidates for spaying since they are lower surgical risks. Each mare’s health and temperament should be evaluated individually.

    Impact on Temperament and Behavior

    Most mares become calmer and more relaxed after being spayed. They no longer show signs of coming into heat and do not attract attention from stallions. This change is often appreciated by owners!

    However, a small percentage of mares may become more irritable or bad tempered after spaying. This seems more likely in dominant mares. Owners notice increased nipping, kicking out, or aggression issues. Patience and gentle but firm discipline is required to retrain such mares after spaying.

    On the whole, mares in a herd situation get along better without the hormone fluctuations. Less fighting over food and attention from geldings may be observed. Yet spayed mares may still challenge each other to determine herd hierarchy.

    Proper nutrition, exercise, training, and herd management remains important even after spaying. But most mares should experience reduced drama and stress, benefiting their health and disposition.

    Alternatives to Fixing Female Horses

    Hormonal Supplements

    There are several hormonal supplements available that can help deter estrus cycles and behaviors in mares without surgically fixing them. These supplements aim to suppress the production and release of reproductive hormones like estrogen and progesterone to prevent the mare from coming into heat.

    Two common oral supplements used are altrenogest (brand name Regu-Mate) and medroxyprogesterone acetate (brand name Depo-Provera). When administered daily, these prostaglandin inhibitors can prevent estrus for several months.

    Long-acting injections or implants that steadily release progesterone over time are another option. Studies show hormonal supplements are 80-90% effective at suppressing estrus in mares. While quite reliable, some mares may still occasionally demonstrate heat signs or get pregnant while on these supplements.

    They also require administration daily or replacements every few months, making them less convenient than one-time surgical sterilization.

    Separating from Stallions

    Another non-surgical option is to simply separate mares from stallions. If mares are never exposed to stallions or stallion pheromones, they are unlikely to exhibit strong heat symptoms that can disrupt training or performance.

    Many boarding stables house mares and geldings together in fields and do not keep breeding stallions on-site. However, even geldings release male pheromones that can induce mild estrous behavior in mares.

    And facilities that board or train both mares and stallions need to be vigilant about separating them to avoid accidental breedings. Mares should be stabled far from stallions and not share paddocks or pastures where stallions are or have recently been.

    Handlers should also change clothes after handling stallions before working with mares. While diligent separation can prevent pregnancy, it does not suppress the mare’s natural reproductive cycle or frustrate normal heat behaviors.

    So this approach is most practical in specific settings like all-female boarding barns.

    Temporary Contraceptives

    There are also several temporary contraceptive options for mares that do not eliminate estrous cycles but prevent pregnancy when applied properly. Common choices include intrauterine glass or plastic ball devices, injectable progesterone, and suture materials.

    When placed by a veterinarian, an inch-diameter ball in the uterus during estrus can prevent sperm from reaching the oviduct to fertilize an egg. However, the mare needs to be monitored for displacement of the device and it must be removed and replaced every cycle.

    Progesterone injections administered within 48 hours of ovulation can disrupt fertilization or implantation of an embryo. But timing is critical. Finally, suture materials like nylon coils threaded through the oviducts can scar over to block passage of eggs.

    This approach requires a more invasive standing flank laparoscopy procedure. Such techniques are 65-85% effective in preventing pregnancy in mares for one season but allow normal estrous cycles to continue.

    The contraceptives need to be reapplied annually which adds cost and inconvenience compared to one-time ovariectomy procedures.

    Caring for a Fixed Mare

    Diet and Nutrition

    Proper nutrition is crucial for the health of a spayed horse. Though their caloric needs are somewhat reduced after being sterilized, fixed mares still require a balanced diet rich in roughage, vitamins, and minerals (thehorse.com).

    Many veterinarians recommend continuing to feed a fixed mare a diet similar to intact broodmares to help maintain muscle tone and a healthy body condition. High quality hay and/or pasture should make up the bulk of her diet.

    Grain concentrates, vitamins, and supplements may be added as needed to reach optimal weight.

    Exercise Needs

    Fixed mares have similar exercise requirements as intact equines. Regular workouts through riding, driving or lunging helps prevent obesity, joint issues, and behavioral problems. On average, 30-60 minutes of exercise per day is ideal.

    For show or competition horses, more intensive conditioning may be needed to reach peak athletic form. It’s important to monitor a previously pregnant mare for signs of postpartum complications for several weeks after she has been spayed before resuming normal work.

    Ongoing Health Monitoring

    Routine vet checks, dental exams, deworming, and hoof care are vital for any horse, including fixed mares. Special attention should be paid to changes in temperament or usual habits, as subtle behaviors can sometimes indicate the early stages of medical issues.

    Possible long-term impacts of spaying mares continues to be researched, but owners should monitor for urogenital problems, increased risk of certain cancers, and other adverse effects reported in limited studies so far (ncbi.nlm.nih.gov).

    With attentive preventative care and husbandry, most veterinarians expect spayed mares to lead normal, healthy lives.


    We’ve covered everything you need to know about spaying female horses, from what ‘fixing’ means to the procedure itself to aftercare for the mare.

    While spaying comes with risks like any surgery, it may be recommended for health, temperament or population control reasons. Talk to your vet about whether it makes sense for your particular mare and situation.

    With proper pre- and post-operative care, most mares recover fully and can live a happy, healthy life after being fixed. Work closely with your veterinarian if you decide to have your mare spayed to ensure the best outcome.

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