06/17/2026
Over the past few years, I have spoken with a number of horse owners and breeders who have experienced foals affected by congenital hypothyroidism dysmaturity syndrome (CHDS) and related developmental disorders, including lack of a suckle reflex, difficulty nursing, inability to stand on their own, seemingly weak or unstable joints, contracted tendons, underbites, delayed ossification, long gestations, weak or dysmature foals, and other developmental concerns.
Many people choose to keep these experiences private, which I completely respect. However, because these cases can feel isolating and overwhelming, I wanted to make this post for anyone who may be dealing with similar challenges.
Research led by Dr. Claire Card and her team at the Western College of Veterinary Medicine (WCVM) has identified important links between mare nutrition during pregnancy and thyroid function in both mares and foals. Their work has shown that iodine and selenium deficiencies may be more common than many horse owners realize, and that factors such as nitrates and glucosinolates (compounds found in some weeds and forage plants, including mustard-family plants) may interfere with normal thyroid function. Studies conducted on Canadian horses found a significant number of mares and foals with marginal or deficient iodine levels, and many mares tested were also selenium deficient.
The research suggests that adequate iodine and selenium status during pregnancy are important for normal fetal development and thyroid function. While not every developmental issue is caused by mineral deficiencies, this area of research continues to demonstrate how critical proper nutrition is during gestation.
This topic is especially important to me because this year I had a foal personally affected by this syndrome. His name is Frosty, and like many owners facing this diagnosis, I was searching for answers.
Since his birth, I have been working closely with my veterinarian, Dr. Good, and my farrier, Kenny Price of KP Horse Shoeing as well as personal contact with Dr. Card. Together, we have developed a plan for Frosty and have been encouraged by the progress he has made. The attached photos were taken just 7 days apart and show the improvements we have seen through early intervention, careful management, and a dedicated team approach. The mare had 24/7 access to a primarily selenium based salt block through pregnancy and now through lactation. I am learning that this was not even touching the surface of this problem.
What I've learned through Frosty's journey is that there is hope. There are answers. There are people willing to help.
Through splinting, corrective shoeing and Vitamin E./Selenium injections, stall rest, controlled and intentional movement, Frosty has made huge progress and is straight legged, and 100% independent of human intervention now.
In addition to my own experience, I have worked closely with 13 affected foals from different owners, breeding programs, management styles, and feeding programs. While every case is unique, there are common themes, valuable lessons, and treatment strategies that can make a meaningful difference.
I am not a veterinarian, and this post is not intended as medical or nutritional advice. Every horse, farm, forage source, and management program is different. If you have concerns about your mares or foals, I encourage you to work closely with your veterinarian and nutritionist.
What I do want people to know is that if you are facing this syndrome, you are not alone. Whether you have questions about diagnostics, mineral testing, forage analysis, hoof care, supportive management, or simply need someone to talk to who understands what you're going through, please feel free to reach out to me privately.
There is absolutely no judgment. Many of us are learning together, and the more information we share, the better equipped we are to support healthy mares and healthy foals.
If you are dealing with an affected foal and would rather not discuss it publicly, my inbox is always open. I am happy to share Frosty's story, what has worked for us so far, and what I continue to learn each day.
Sometimes knowing you're not alone is the most important part.
Special thanks to Dr. Claire Card and her research team at the Western College of Veterinary Medicine for their ongoing work investigating CHDS, thyroid health, iodine deficiency, selenium deficiency, and developmental disorders in mares and foals. Their research is helping horse owners and veterinarians better understand this complex syndrome and provide affected foals with the best possible chance for success.
We will be hosting a video seminar with Dr. Card who will be educating anyone interested in attending. If you are interested in the seminar please reach out to me.
