Breeding (Stallion) in Horses

Breeding (Stallion) in Horses - Symptoms, Causes, Diagnosis, Treatment, Recovery, Management, Cost
Breeding (Stallion) in Horses - Symptoms, Causes, Diagnosis, Treatment, Recovery, Management, Cost

What is Breeding (Stallion) ?

There are many factors involved with the success or failure of your breeding stallion, many of which can be assessed well in advance of the actual breeding date. These factors can include physical conditions, behavioral characteristics, and genetic predispositions. Some physical conditions, such as obesity and pain from untrained muscles, can be corrected with proper diet and exercise, while other conditions, such as genetic predispositions to low sperm count or motility, may require specialized treatments.

Breeding horses should be undertaken with care and forethought. Stallions, as well as mares, should be confirmed to be in good health and condition before fertilization occurs.

Symptoms of Breeding (Stallion) in Horses

The signs of infertility in a stallion are uncovered when the horse’s ejaculate is assessed. When evaluating semen, examiners frequently analyze two samples that were collected at least one hour apart and investigate the following three criteria. 

  • Motility - Motility refers to the sperm's ability to move forward in a straight line. Ideally, 60-70% of the sperm cells should be motile
  • Quantity - This number can vary based on the season, the size of the stallion's testicles, and the horse’s age; amounts of sperm in the 10-20 billion range per sample are sufficient, although the second test will typically reveal just half the amount of sex cells that the first sample contained
  • Structure - At least 50% of the spermatozoa observed should be structurally sound. 


In most cases of artificial insemination, the semen is collected from the horse using a “phantom”, a padded metal frame that is used in place of a live mare, then processed as needed for transportation and dispensation to the chosen mare. It can either be transported fresh, cooled, or frozen. 

  • Fresh - In order to employ fresh semen, the stallion and mare must be at the same location as the stallion so that the semen can be infused directly into the mare after it has been evaluated for indicators of fertility
  • Cooled - Cooled semen will be viable for 48-72 hours, and is typically prepared by running the ejaculate through a centrifuge to remove seminal plasma; an “extender” substance is then added to the remaining material, and it is cooled to four or five degrees Celsius before transportation
  • Frozen - Frozen semen is gaining popularity, and is prepared by freezing the semen in liquid nitrogen at a temperature of -197 degrees centigrade; freezing the sample allows for indefinite storage, however, around typically around 30% of the sperm viability is lost in the process


Causes of Breeding (Stallion) in Horses

There are several reasons that your stallion may have decreased sperm counts or motility. 

  • Age - Young studs, in the two to three-year-old range, have narrower scrotums than more mature males, and generally, have a smaller daily sperm output; stallions may also experience decreases in libido as well as sperm production and motility as they age
  • Environmental - Certain weather conditions, toxins, and chemicals can have a negative impact on semen quantity and quality; changing the problem environment should reverse the issue
  • Genetic - Subfertility can be passed down from stallion to stallion
  • Pain- Back injuries, pelvic damage, and any chronic pain may make breeding of any sort unpleasant for the animal, which may reduce his overall libido
  • Seminal Plasma Deficiency - The motility of sperm can be significantly affected by the seminal plasma, although the mechanisms which make seminal plasma detrimental or beneficial to the sperm are poorly understood
  • Venereal Disease - Sexually transmitted disease can cause testicular dysfunction, which is usually reversed by treating the underlying illness


Diagnosis of Breeding (Stallion) in Horses

A visit with the equine veterinarian well in advance of the actual breeding is crucial in ensuring the best outcome. The examiner will start by checking the stud’s physical health, certifying that the horse’s weight and condition are suitable for the rigors of breeding and evaluating physical components such as the health of the teeth, the condition of the horse’s hooves, and size of his testicles. The horse’s semen will also need to be evaluated for sperm count, motility, and physical soundness of the sperm cells.

If the mare is to be fertilized using cooled or frozen semen, then the veterinarian may also process and test the specific stallion’s ejaculate to ensure that the majority of the sperm cells survive the process. Samples will also be taken for testing to confirm that no venereal diseases can be transmitted to the mare, including Equine Viral Arteritis, Contagious Equine Metritis, and Equine Herpesvirus-3. Screening tests for certain genetic diseases are also required, in an attempt to eliminate dangerous disorders like Polysaccharide Storage Myopathy, Lethal White Overo, and Malignant Hyperthermia.



Treatment of Breeding (Stallion) in Horses

There are several conception techniques available to the modern horse breeder, all but live cover can use either fresh, cooled or frozen semen. These can include: 

  • Live Cover - Live cover is done by allowing the the stallion to breed directly with the mare; in order to avoid injury to the horses and the people involved, this should be handled by someone with training and experience working with live cover breedings
  • Artificial Insemination - Artificial insemination is now approved by almost all breed registries, but Thoroughbreds conceived through this method are not eligible to be registered for racing; in certain circumstances, this technique prevents injury for horses and humans and may reduce the chances of uterine infection, but it does require a veterinary surgeon or artificial insemination technician to complete
  • Intracytoplasmic sperm injection - Individual sperm cells from the stallion are injected directly into an egg from the mare and the egg is then matured for six to nine days in a laboratory, then transferred to a recipient mare for gestation; this can be useful for stallions with low sperm counts or poor motility


Worried about the cost of Breeding Stallion treatment?

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Recovery of Breeding (Stallion) in Horses

Although injuries during breeding are rare, they do happen, in either live cover or collection for artificial insemination. Some of the more common injuries that can occur to studs during breeding include:

  • Damage to penis due to obstruction - This can happen when there is an obstruction to the vaginal opening, such as tail hairs across the lips of the vulva
  • Kicks from the mare - In some situations, the mare may be less than receptive to the stud’s advances, and kicks can occur
  • Swelling of the penis - This can be caused by a number of sources of painful swelling of the penis or foreskin although improperly fitted rings or bands in the artificial vagina are most common


Breeding (Stallion) Questions and Advice from Veterinary Professionals

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