Interview - Jos Mottershead


In a recent interview, Jos Mottershead, owner of, LLC, explained some of the key components breeders need to be prepared for the upcoming breeding season. As part of this discussion, Jos mentions several important products and equipment, provided by IMV, that are a critical component for breeders to have on hand.

It is recommended that owners conduct a yearly breeding soundness evaluation on their stallion in advance of the onset of the active breeding season. There are generally four components to this examination:

  1. An overall physical exam
  2. An examination of both the external and internal reproductive organs
  3. An examination for bacterial presence
  4. Semen collection and evaluation


1. Physical Exam

The overall physical exam is intended to review conditions which may not be specifically linked to the reproductive aspects of the animal, but which can impact them. Examples of these conditions can include arthritic changes to the back, hips or stifles of older stallions. These issues may result in a problem during mounting.


2. Examination of the External and Internal Reproductive Organs

The evaluation of the external and internal reproductive organs monitors changes from year-to-year. Routine manual palpation of the testicles can identify changes, such as degeneration or neoplasia, and these types of conditions could suggest a need for modification of a stallion’s “book” if sperm numbers are likely to be reduced. Both testicles should be fully descended and uniform in size (there is a positive correlation between testicular size and daily sperm output). Likewise, a stallion with unilateral cryptorchidism can still be fertile, but may pass this undesirable trait on to offspring. Internal evaluations of the genitalia, inguinal rings, and aorta and iliac vessels are evaluated by rectal palpation and ultrasonography. 


3. Examination for the presence of sexually transmissible disease

Another aspect of evaluation which is commonly overlooked is that of the presence of bacteria or other infections in the reproductive organs. With some sexually transmitted diseases, the stallion is merely a carrier and exhibits no clinical signs of disease. Swabbing of the penis and performing a culture is valuable for confirming the absence of potentially sexually-transmitted bacteria. For more information on sanitary control products, contact IMV.

These are the three confirmed sexually-transmissible bacteria:

  • Taylorella equigenitalis
  • Klebsiella pneumoniae
  • Pseudomonas aeruginosa


More often than not, when the above mentioned bacteria are passed from the stallion to the mare, trouble can follow in a variety of reproductive issues, from endometritis to a loss of pregnancy.

A sexually-transmitted viral disease is Equine viral arteritis (EVA) which is a contagious disease of horses caused by the equine arteritis virus (EAV), an RNA virus that is found in horse populations in many countries. While typically not life-threatening to otherwise healthy adult horses, EVA can cause late term abortion in pregnant mares; uncommonly, death in young foals; and establish a long-term carrier state, particularly concerning in breeding stallions. This disease needs to be managed and identified prior to the possible exposure. Stallions are the natural reservoir for the virus, which is maintained in the secondary sex glands. It is then shed in the semen and can infect mares at the time of breeding. As it is a virus, it is not affected by antibiotic present in semen extenders, and will also not be destroyed by freezing. Consequently, it can be transmitted via cooled or frozen semen, as well as fresh. It is first and foremost a respiratory disease and thus can also be transmitted via the respiratory route in acutely infected animals of all sexes. The disease can be easily managed, in particular with vaccinations where suitable and permitted, but one must be aware of the disease’s existence and respond appropriately to ensure safe breeding practices. A blood test will identify sero-positive stallions, but that merely means that they have been exposed in some manner (including via vaccination), not that they are infectious. A sero-positive stallion with no record of recent vaccination should have semen collected and sent to a lab for virus isolation testing. For ethical marketing, EAV-shedding stallions will require slightly different protocols be performed on mares prior to receipt of semen. It is illegal to ship EAV-positive semen into some states, while others require licenses.


4. Semen Collection and Evaluation
This component of an examination is self-explanatory, as breeders obviously wish to confirm acceptable numbers of progressively motile and morphologically normal sperm in an ejaculate. Other parameters worth reviewing include total daily sperm output and recovery time. For a stallion in a cooled transported semen program, an annual comparison of extenders for suitability is recommended.

So, what if your stallion has a semen quality problem? A wide variety of procedures can be used to improve semen quality. One example being the use of Maxifreeze with centrifugation to assist in altering and improving semen quality. If you have any questions about centrifuges, contact IMV to learn more about our available options!

Evaluating a Variety of Semen Extenders for each Stallion

This is critical, because not all semen extenders will work for all stallions, and not all stallions will work in all semen extenders. By “work”, we are typically referencing maintaining adequate sperm progressive motility levels, although truly we should be considering fertility rather than motility. The two are not completely related – although of course if there is no motility, then fertility is more likely to be compromised. At, LLC, we annually evaluate the semen for stallions standing with us for suitability in a variety of different extenders, and we recommend our clients do the same. This is of particular importance if offering cooled transported semen.

Even though there is no single semen extender which will produce good results with all stallions, we have found that INRA '96 does work well with a high percentage of stallions. In our pre-season evaluations of stallions standing at our facility for extender suitability, we collect, pack and evaluate in 7 different extenders, and each season INRA '96 produces excellent compatibility with many of those stallions. We also use it as a "random use" extender, when we are presented with a stallion with no known extender history and no opportunity to run tests prior to collection and shipment, and have good results even in those circumstances.

Important Final Tips for Stallion Breeders for the 2017 Breeding Season

One of the most important points is to be proactive and plan ahead! Make sure that you are knowledgeable about managing stallions and semen and if you are not, seek reliable information on the subject before offering the stallion to the public.

Be critical of semen parameters. Most people do not have access to a Computer Assisted Sperm Analysis System (CASA), and thus rely on “eyeballing” sperm under the microscope and estimating motility values. In general, with visual estimates, total motility values are usually close to those obtained by CASA when estimated by a technician or practitioner with years of experience in stallion reproduction, but progressive motility values are typically over-estimated! Anything over 50% progressive (using settings provided by Hamilton Thorne on their IVOS II (Ref. 024911) and CEROS II (Ref. 024904) units) is excellent. Most “good” evaluations will be in the 40-50% progressively motile range.

With a Hamilton Thorne CASA unit, one great benefit is the ability to obtain a sperm concentration value. While motility evaluations can be performed on the CEROS CASA using regular microscope slides and cover slips, to achieve accurate counting ability, a known volume of semen must be used. We use Leja cells for this purpose. These are simple to use, being loaded with a pipettor or syringe, but automatically stabilizing the volume internally by using capillary action to achieve the exact filling amount each time. We have tried other fixed-volume slides, but have settled on Leja Cells as being the simplest and most convenient to use.

Treat and handle your stallion fairly. If you’re not comfortable handling a stallion, don’t. Not everyone is, and that’s fine! Simply stand the stallion at a facility where he can be managed well.

Be aware that there are many “wives’ tales” related to equine reproduction as a whole, not only stallions. Research accurate and reliable sources, and don’t pass on the wives’ tales!

Finally, enjoy what you’re doing! If you don’t enjoy working with horses, or don’t have the patience for it, don’t do it. Insisting on doing it regardless will cause everyone to suffer – the horses, your co-workers, your clients, your family and yourself!

Many thanks to Jos for sharing his experience with our IMV audience!

Please visit their website to explore the various tools available to you. One of those tools we’re featuring today is the semen extending calculator

Semen Extending Calculator: A valuable tool for breeders! The Semen Extending Calculator performs the calculations and provides comments and suggestions when extender ratios and total sperm numbers are too low. It also has the ability to produce a report suitable for printing to send with your semen shipments. 

Semen calculator