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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.
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
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
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
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
Genetic - Subfertility can be passed down from stallion to stallion
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
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.
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
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
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
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
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