Leading journal calls for more research into reproductive problems in mares

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A leading international equine science journal is calling for more research to address reproductive problems in broodmares.

The Equine Veterinary Journal has made 10 papers in the field of equine reproduction available online for a year in the hope they will not only inform and educate, but inspire interested parties to conduct further studies to build knowledge and expertise.

While there have been significant advances in equine reproduction techniques in recent years there has been a shortage of research on reproductive problems in broodmares.

The papers were selected by equine reproduction expert Jon Pycock, who has just been elected president of the British Equine Veterinary Association.

Equine reproduction is important in equine veterinary medicine both in practical and commercial capacities.

There have been significant advances in both natural breeding and artificial breeding techniques. Artificial insemination success rates have improved; embryo transfer has become a common procedure and advanced techniques such as intracytoplasmic sperm injection (ICSI) are now being used with success.

Jon Pycock
Jon Pycock

Equine stud medicine currently accounts for a significant proportion of veterinary business.

Pycock, who has spent most of his professional career working in the field of equine reproduction and broodmare management in particular, put together five tips for breeders to help with safe, effective and healthy breeding.

  • Work with a veterinary surgeon experienced in the field of equine reproduction who is prepared to discuss all aspects of the process with you.
  • Be a well-educated client. As a veterinary surgeon I have always viewed the best clients as those who are well-educated. This does not mean classifying yourself as an expert because you have read a random article that you found online. Rather you will have thought very carefully about what the breeding process entails, read some information written by knowledgeable colleagues with the experience to write well-informed articles, discussed the process with your vet and maybe even attended a lecture or two on the subject.
  • Have a good reason to want to breed from your mare and be prepared to commit both time and money to the process.
  • Make sure your mare is healthy and free from any disease before breeding.
  • Be an optimist and prepared for occasional disappointments along the way.

Although there is a lack of research on reproduction and broodmares, the quality and innovative nature of the 10 papers, all of which have been published over the past four years, present a valuable information source.

One paper deals with transient post breeding endometritis in susceptible mares, which can adversely affect pregnancy rate. One of the articles in the collection reviews the current research on inflammatory mechanisms of endometritis, focusing on endometrial gene expression.

Another paper evaluates the roles of corticosteroids and immunomodulators in the control of inflammatory response to prevent post breeding endometritis.

A further study looks at the systemic treatment of infectious endometritis using the respiratory treatment cephalosporin.

Despite a lack of scientific evidence, many vets regularly use exogenous progestins in the belief that it reduces the incidence of early pregnancy failure. A speculative report in the collection describes a pregnancy that was successfully rescued possibly because of the administration of oral altrenogest, which could represent a documented case of luteal insufficiency.

Fertility in mares declines with age but the various reasons for this remains poorly understood. One of the studies has found a positive correlation between Anti-Mullerian Hormone (AMH) concentration and Antral Follicle Count (AFC) concentration in older mares and concludes that AMH concentration may be a better reflection of reproductive age than calendar age.

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The Equilume Light Mask provides the optimum level of timed blue light to a single eye to deliver all the benefits associated with long summer days.

Horses are known to be ‘long day breeders’ but artificial light in stables or barns is commonly used to further advance the Thoroughbred breeding season. One of the papers describes the use of individual light masks, similar in design to racing blinkers, which enable the mares to remain outside. This has cost, management and welfare advantages.

Relatively little is known about the equine oviduct, despite it playing a fundamental part in the fertilisation process. One paper in the collection explains the novel technique of hysteroscopic hydrotubation of the oviduct via the uterotubal junction, which could present an easier way to investigate oviduct function and any abnormalities.

Twin pregnancies are extremely common in clinical practice and one conceptus is usually reduced manually. However, little is known about the effects of the crushing procedure on the live foal. The study identified that in mares of more than nine years of age that had undergone a manual twin elimination the live foal rate was less than in similarly aged mares with a single conceptus.

While anovulatory haemorrhagic follicles are the most common ovarian abnormality in the mare the causes are, as yet, unknown and treatment is limited. One of the studies demonstrates the ability of prostaglandins to eliminate the stimulated induction of anovulatory follicles.

Various therapeutic options have been explored to repress oestrus-associated behaviour in mares, including a GnRH vaccine. However irreversible suppression of reproductive function is not usually desirable. One of the studies found that the vaccine is reversible although it took longer in younger mares and in some cases could take as long as 720 days.

“Together, the papers in this online collection provide insight on a number of the clinical challenges currently facing veterinarians involved in broodmare practice,” said journal editor Celia Marr.

“Numerous gaps in knowledge remain, and to counter this the EVJ intends to continue to publish important and relevant studies in this field. In future years we hope to see an increase in quantity of pertinent studies to match the undoubted quality of the reproductive research in this collection.”

The collection is available free online here

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