Below, please find links to all of the clinical trials currently accepting equine patients. The studies are organized by discipline and include a multitude of information, including (but not limited to) the study’s purpose, benefits for participating, and financial incentive information.

If you have any questions, please contact the individual outlined at the end of each trial summary.  For information about the services provided by the Veterinary Medical Teaching Hospital, please visit the Equine Services page through the Large Animal Clinic of the hospital. If you would like more information regarding equine research, education and public service, please contact our Center for Equine Health.

Hoof Wall Separation Syndrome (HWSS): Understanding the Genetics

Title: Hoof Wall Separation Syndrome in Connemara Ponies

Purpose of Study: Hoof Wall Separation Syndrome (HWSS) is an inherited condition seen in Connemara ponies and typified by the dorsal hoof wall splitting away from underlying structures. The condition results in afflicted ponies having to support weight on the sole of the hoof instead of the dorsal hoof wall, causing severe pain and a diminished quality of life.

HWSS is particularly troubling for the Connemara community because the parents of affected ponies are themselves completely unaffected.  Investigation into the underlying genetic cause of HWSS has the potential to inform these breeding decisions, and could also provide insight into the disease pathophysiology. Sequencing of candidate genes within a specific region on the genome is currently underway, and any functionally relevant genetic differences identified will be validated using a larger sample set.  

Participation Requirements: Connemara ponies diagnosed with Hoof Wall Separation Syndrome

Initial Evaluation for Participation: Please contact Carly Stevens ( or Miriam Aguilar ( to confirm disease presence.

Procedures: The only procedure required is the collection and submission of a DNA sample. Please contact Carly Stevens ( or Miriam Aguilar ( for information about how to submit samples. 

Benefits: There is no direct benefit of this study for you or your pony at this time; however, development of a DNA based test will allow breeders to make informed breeding decisions.

Owner Responsibilities: The owner or referring veterinarian needs to collect and submit a DNA sample.

Contact: Carly Stevens ( or Miriam Aguilar ( for more information.

Eyes (Ophthalmology)
Recurrent Uveitis: Assessing a Stem Cell Therapy

Title: Efficacy of Autologous Mesenchymal Stem Cells for Treatment of Equine Recurrent Uveitis Following Intravenous Injection

Purpose: Equine recurrent uveitis (ERU) is caused by inflammation of the uveal tract of the eye and is the most common cause of blindness in horses. ERU often involves lifelong medical therapy or surgery, which holds the potential for a variety of potentially serious complications. Because fat-derived stem cells are known to regulate inflammation and facilitate tissue repair, we wish to investigate the effectiveness of a new stem cell therapy for ERU and to better understand how stem cells work to limit inflammation. This treatment has the potential for being relatively non-invasive and removing the need for lifelong treatment.

Participation Requirements: Horses who have had multiple episodes of anterior uveitis within the last 12-18 months. The MSCs will be injected intravenously either during a period of inflammation or during a quiescent period.

Initial Evaluation for Participation: Horses that are candidates for inclusion into the study will be examined by a board certified veterinary ophthalmologist. This examination will determine if the horse has evidence of current or past uveitis.

Procedures: The trial procedures include the following:

  • Your horse will be sedated using common sedatives for each treatment. Local anesthetic will be used to provide optimal pain management for fat removal in addition to sedation.
  • A small amount of fat from an area near the tail of your horse will be removed in order to isolate and culture the MSCs. Your horse will be admitted for fat removal and monitored prior to its discharge home (likely the same day).
  • Two weeks after fat harvest, your horse will receive its first course of therapy, which involves an intravenous infusion of 50 million MSCs.
  • Two weeks after the first MSC treatment, your horse will receive a second injection of 100 million MSCs. At this time, your horse will be clinically examined and about 2/3 of a cup (60 mL) of blood will be collected.
  • Two weeks after the second round of injections, we will need to see examine your horse again. At this time, your horse will be clinically examined and about 1 tablespoon (10mL) of blood will be collected.

Benefits: The study will pay for costs associated with the ophthalmic examinations and interpretation, fat harvest and MSC expansion, and consecutive visits and therapy will be paid by the study. You (the owner) are responsible for treatments associated with any side effects incurred by your horse’s participation in the study.

We cannot promise any benefits to your horse or other animals from your taking part in this clinical trial; however, possible benefits include the potential of your horse achieving a state of remission without the use of long-term cyclosporine therapy Moreover, this study may help us to further target specific use of MSCs for other horses that suffer from ERU.

Owner Responsibilities: You will be required to bring your horse to the VMTH once for fat collection and twice for stem cell therapy. The ten horses comprising this study are client owned and will be returned to their owners two weeks after the 2nd injection. The animals will be examined every three months for up to 18 months following the study.

Contact: Dr. Steve Hollingsworth at

Fertility: Understanding subfertility in older maiden mares

Title: Endometrial biopsy-related changes in older maiden mares

Purpose: Older, maiden mares have a reputation for being subfertile. It has been shown that maiden mares older than 13 years have reduced fertility compared to mares that have had previous foals. The specific reasons for the reduced ability to become pregnant and maintain a pregnancy are unknown. This study aims to compare biopsies from the uterus of older maiden mares with mares of comparable age to look for detrimental changes that can explain the drop in fertility. Knowing specific causes of subfertility allows targeted treatment to help increase fertility.

Participation Requirements: Mares that are older than 12 years old and have either:

  • Not had a pregnancy in the last 6 years; or,
  • Have had consecutive pregnancies for 5 of the previous 6 years, including the most recent year.

Initial Evaluation for Participation: None.

Procedures: The trial procedures include the following:

  • A transrectal ultrasound evaluation will be performed to determien the stage of estrous cycle of your mare.
  • Your mare’s tail will be wrapped and tied to the side. The vulvar area of your mare will be washed with a mild detergent and dried off.
  • The veterinarian will put on a sterile sleeve and insert a sterile biopsy instrument (70 cm long, alligator-type biopsy instrument with 20 x 43 mm sample basket) that is guided through the cervix with the gloved hand. Once in the uterus, the biopsy instrument is opened. The hand is withdrawn from the vagina and inserted into the rectum. The open instrument is palpated per rectum and the endometrium is gently pressed into the open instrument. The instrument is closed and withdrawn from the uterus.
  • The mare’s vulvar area is cleaned with water.
  • If your mare was determined to be in diestrus (out of heat), an injection of prostaglandin will be given to bring the mare into heat and avoid an inadvertent uterine infection.

NOTE: Mares do not usually require sedation for the procedure; however, if your mare is uncomfortable standing still in the equine stocks or nervous, we will sedate your mare with xylazine (a short-acting sedative given intravenously). Additionally, mares do not usually require pain medications for this procedure because the inner lining of the equine uterus does not contain sensory innervation.

Benefits: We cannot promise any benefits to your mare or other animals from your taking part in this clinical trial; however, possible benefits include specific knowledge about any uterine disease in your particular mare. This will be potentially be very useful in formulating a breeding management plan for your mare, should you decide to have her bred. Your mare’s participation will also help us better understand age-related and parity-related (number of foals a mare has in her life) changes in a mare’s uterus that can affect the ability to maintain a pregnancy.

Owner Responsibilities: If you allow your mare to participate in this study and desire to have the results for your own personal use, you will be responsible to pay for a board-certified pathologist to evaluate the biopsy. No charge will be assessed for taking the biopsy, only for the interpretation of the results. If you do not desire to have the results for your own use, you will not have any financial responsibility; however, the results will not be given to you.

Contact: Dr. Bruce Christensen, DVM, MS, DACT at or (530) 752-0292

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If you cannot find what you are looking for, please email us or call (530) 752-5366.