foal and mare after successful horse breeding

Breeding Horses

Considerations for breeding horses

Breeding horses is big business in the horse industry. The right bloodlines can fetch substantial dollars and lead to successful racing and show horses or perfect matches for amateurs. However, irresponsible or thoughtless breeding creates more unwanted horses needing homes. Following is an explanation of the process and some things to consider before breeding a mare or stallion.

Factors to consider before breeding horses

To decide whether or not to breed your horse, consider the health and soundness of the potential sire and dam. Review the medical history of the stallion and mare with a veterinarian to ensure there are no genetic issues that could be passed on, like HYPP, PSSM, and others. Also discuss conformation, behavior, and other factors that may impact the success of a specific pairing with your veterinarian. Responsible breeding is crucial.

foal resulting from successful horse breedingOptions for breeding horses

Once you have selected the mare and stallion, you will choose from three options for breeding:

With live cover, two horses are brought together and physically bred to each other. The benefits of live cover are that it requires less equipment, the sire is guaranteed, and the breed cannot be dominated by a few stallions. Some (but not all) experts believe live cover has a higher conception rate than artificial insemination.

With artificial insemination (AI), semen from a stallion is introduced into the mare’s reproductive tract during her estrous cycle. The benefits of AI are that cooled or frozen semen can be shipped anywhere. The mare and stallion do not have to be at the same farm. AI also reduces the risk of injury and the spread of disease. Using AI extends the breeding season and allows stallions to continue competing.

With embryo transfer (ET), performance mares can continue competing. The donor mare is bred; about a week later the embryo is removed and transferred to a surrogate. The surrogate carries the pregnancy, foals, and nurses the foal. 

Neither AI nor ET is allowed in thoroughbreds in the United States.

What to expect when breeding horses

After you choose a breeding option, have your veterinarian give the mare a complete physical examination. This includes a thorough reproductive exam to ensure she is healthy enough for pregnancy. This process is known as a breeding soundness evaluation or BSE. The stallion should also be examined.

Track your mare’s estrous cycle to know the best time to breed. As she gets closer to ovulating (releasing an egg from the ovary), the veterinarian will perform multiple rectal palpations to feel for egg-containing follicles on the ovary. An ultrasound may be used to see and measure the size of the follicles at each visit. Between the mare’s behavior and the size and softness of the follicles, breeding(s) can be planned fairly accurately. In some cases, hormones are used to coordinate the estrous cycle.

As early as two weeks after breeding, the veterinarian can use rectal palpation and ultrasound to see if the mare conceived. They will check the entire uterus to ensure there is only one embryo since twins in horses can lead to complications. Additional exams and tests may be performed at key dates during the pregnancy, especially if the mare is older or has had problems in the past. The fetal gender can be determined between days 110 and 130.

What to expect in the pregnant horse

The average equine pregnancy is 330 to 340 days (11 months), but can range from 320 to 370 days (more than a year!) and still be considered normal. During this time, work closely with a veterinarian to monitor the mare’s health and keep up with preventive care such as vaccinations, parasite control, hoof trimming, and dental care. There are also specific recommendations for inoculation and deworming during pregnancy and before foaling.

Proper nutrition for the pregnant mare is also important to producing a healthy foal. Mare owners should consult a veterinarian or equine nutritionist for advice on what to feed, how much, and how often. Each stage of pregnancy in the horse – early, middle, and late – has its own daily nutrient requirements.

Is there a role for supplements in breeding horses?

For stallions, research shows that omega-3 fatty acids (especially DHA) and antioxidants may positively affect sperm count and motility (movement). Reproductive experts stress the importance of providing both water-soluble antioxidants (like Vitamin C) and fat-soluble antioxidants (like Vitamin E). Since Alpha Lipoic Acid is both water-soluble and fat-soluble, it’s a good choice for an antioxidant for stallions.

For mares, energy, protein, and mineral needs don’t increase until the fifth month of pregnancy once the fetus starts rapidly growing. Until then, nutrients to ask the veterinarian or nutritionist about supplementing include the antioxidants Vitamin A and E, as well as the mineral Selenium. According to research, optimal levels of Selenium throughout pregnancy support a healthy immune system in foals.

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