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Home:Equine Diseases:Infertility

Equine Diseases


Equine Infertility is a very common reproductive problem. It is particularly relevant where horse breeding is a source of income. Studies show that the equine infertility rate under human management is very high whilst equine infertility does not appear to be problematic in the wild.

Equine Infertility can be broken down into three different categories - (a) the mare does not have a cycle (b) the mare has a cycle but does not conceive or (c) the mare has a cycle, conceives but then suffers early embryonic death (EED).


Identification of the causes of equine infertility can be very difficult but some of the following may be identified. Some of the causes can apply to both the mare and the stallion and others to either the mare or the stallion.

•  Endometriosis - cells that normally grow inside the uterus (womb) instead grow outside the uterus

Endometritis - any inflammation of the uterine lining

•  Uterine infection – the main bacterium is Streptococcus zooepidemicus

•  Age of the mare – infertility problems become more frequent in older mares particularly over the age of 12 yrs

•  Mares with no apparent problems not settling every time they are bred through a cycle

•  Accumulation of intra-uterine fluid during “the season”

•  Placentitis - an infection of the placenta

•  Breeding the mare too often

•  Ovarian tumors

•  Equine Arteritis Virus (EAV) infection causing abortion after the third month of pregnancy or the death of foals after birth

•  M aking mistakes about the mare being “in season”

•  Breeding off season with no compensating artificial light

•  Stress - affects the hormones needed for fertility

•  Laminitis

•  Lack of proper blood flow to the sexual organs

•  Poor Nutrition

•  Sex chromosome abnormalities

•  Hypothyroidism - the thyroid gland produces an insufficient amount of thyroid hormone causing lowered metabolism

•  Inadequate amounts of functional sperm

•  Low sperm count - not having any measurable level of sperm in the semen

•  Low sperm motility - The ability of sperm to move and swim in a forward direction.

•  Poor sperm morphology - t he size and shape (form) of an individual sperm

•  Testicular trauma or degeneration

•  Contagious Equine Metritis (CEM) – an equine venereal disease caused by the bacterium Taylorella Equigenitalis, which is carried by stallions and causes infertility or abortion in mares.


Consult your vet to have your horse thoroughly examined, firstly for any inhibiting ailments like laminitis and secondly to check your horse's reproductive system. Your vet may also carry out a fertility evaluation test. After this, a diagnosis can be made on the reasons for your equine infertility problem. Treatment will depend on the diagnosis. Some of the following treatments for equine infertility may be prescribed.

•  Hormone injections can help with equine infertility - oxytocin has proven beneficial in sub-fertile mares by stimulating uterine contractions to expel any excess fluid thus increasing pregnancy rates .

•  Deep uterine artificial insemination – because of the “help”, sperm are speeded on their way reducing the incidence of sperm lost on their travels to the egg

•  Hysteroscopic insemination – deeper than above, with sperm deposited at the very edge of the oviduct (tube through which the eggs pass from the ovary to the uterus) giving an even greater chance to a higher number of sperm

•  Gamete Intrafallopian Transfer (GIFT) - a newer technique involving transfer of both sperm and eggs directly into the oviduct.

•  Intracytoplasmic Sperm Injection (ICSI) - When a sub-fertile stallion is the problem , a technique involving injection of a single sperm is injected into an egg ready for fertilisation, then cultured in a laboratory before transfer to the mare.

•  Ultrasonography - can be very effective cases where the mare conceives but suffers early embryonic death (EED

•  Reinfocement Breeding –not yet a validated treatment but has been known to be effective. It involves collecting semen from the exterior of the penis when the stallion dismounts and mixing it with pre-warmed semen extender, then infusing it into the uterus of the mare just covered.

•  Proper management helps prevent equine infertility - A good parasite and vaccination program should be carried out under the supervision of a vet. Particular attention should be paid to de-worming. If stallion infertility is the problem and your stallion lives in a barn with other stallions, low libido could result. Placing your stallion in a strong paddock near mares could help increase libido.

•  Good nutrition - can counteract equine infertility & help ward off stress and related illness. Incorrect feeding can lead to laminitis which can have a serious influence on equine fertility. Omega-3 oils are recognised as a possible nutritional aid to stallion infertility, in particular docosahexanoic acid (DHA).

•  Herbal preparations can help with equine infertility & could be of great benefit for mares. These help stimulate endocrine function which aids equine fertility. There are many formulae available containing herbs such as Blue Cohosh, Chamomile Flowers, Chaste Berry, Bladderack, Vervain and Raspberry Leaves. Preparations are available for stallions to aid in producing healthy semen. You can research these products online and check with your vet for further recommendations.

It is hoped that some of the information will eliminate your equine fertility problems.