The Equine Lymphatic System
The lymphatic system in horses is a complex network of vessels, nodes, and organs that work together to help maintain the horse's health and well-being. The primary function of the lymphatic system is to transport and filter lymphatic fluid, a clear fluid that carries white blood cells, nutrients, and waste products, throughout the body, and is critical for maintaining the horse’s immune system and keeping them healthy.
It is closely connected to the immune system and helps to defend the horse against infections and diseases. When harmful substances, such as bacteria or viruses, enter the body, they are recognized by the immune system and targeted for removal. The lymphatic system plays an important role in this process by picking up these harmful substances and carrying them to the lymph nodes, where they are identified and destroyed by immune cells.
Lymphatic System At A Glance
The lymphatic system includes a number of organs and structures, including lymph nodes, the spleen, and the thymus gland.
Lymph is a colorless fluid containing lymphocytes. This fluid carries oxygen and nutrients to the cells while the lymphocytes attack bacteria in the blood.
Lymph nodes are small, bean-shaped structures that are found throughout the body and act as filters for the lymphatic fluid.
Lymphatic vessels collect cellular debris and excess fluid from all parts of the horse’s body and return it to the lymph nodes for filtering.
The spleen is a large organ located near the stomach that is responsible for filtering blood and removing old or damaged red blood cells. The spleen is the largest mass of lymphatic tissue within the horse’s body.
The thymus gland is located in the chest and plays an important role in the development of the immune system. The thymus, along with the spleen and bone marrow, produces lymphocytes.
Is the Horse’s Lymphatic System Different from Mine?
VERY different! For starters, you (a human) have about 600 lymph nodes in your body, while your equine partner has around 8,000!
There is also a distinct difference in how the lymphatic collector vessels function. These collectors run throughout the body of both humans and equines and serve as the receptacles for cellular debris and excess fluid. Smooth muscle fibers in these collectors transport the contents back to the lymph nodes for filtering.
A research study found that the collector vessels in horses are made up of 40% elastic fibers and have far fewer smooth muscle cells than in humans. This is likely due to the fact that the horse is a prey animal and it’s body was designed to be in almost constant motion.
Wild horses, and horses on pasture may log 3.5 to 5 miles a day (or more) foraging for food. The extra elastic fibers in the horse’s collector vessels act as a kind of natural “compression bandage,” enabling the contents to move out. The additional actions of the fetlock joint and flexion of the hoof apparatus during walking also help to pump the lymph back up the legs and through the system.
“Of all the horse’s biomechanical systems, perhaps one that is least understood or looked at is the lymphatic system. (Current research has) discovered significant differences between the equine lymphatic system and that of the humans, and this has profound implications on the way we need to look at and treat lymphatic problems as well as how we keep and manage horses on a daily basis.” - Rebecka Blenntoft
(Lymphatic) Fluid Doesn’t Flow Uphill On Its Own
In horses, as in humans, the lymphatic system is responsible for maintaining fluid balance within the body. This is important because excess fluid can build up in the tissues and cause swelling or edema. The lymphatic system helps to prevent this by collecting excess fluid from the tissues and returning it to the bloodstream.
But remember the part about horses being designed to stay in almost constant motion? In today’s world, many horses spend their days confined in stalls, with limited physical activity. This can lead to a compromised lymphatic system.
Did you know that horses have no muscles in their lower limbs - below their knees/hocks? Without the natural compression and pumping action generated by walking (almost continually), there is nothing in the horse’s lower limbs to help the lymph vessels move the fluid up to the lymph nodes at the top of the leg. Therefore, a horse that primarily stands for long periods of time is more susceptible to lymphatic issues, the most obvious of which is lower limb edema - or stocked-up legs - caused by excessive fluid build-up resulting in swelling.
Other Equine Health Issues Related to the Lymphatic System
Other health issues resulting from a compromised lymphatic system include:
Lymphangitis - an infection of the lymphatic vessels and nodes, usually as a result of bacterial contamination from a wound. Lymphangitis symptoms include swelling, pain, fever, and lameness.
Lymphoma - this is one of the most common equine cancers, representing up to 14% of all tumors. It can affect any part of the body, affecting all breeds and both sexes.
Immune system disorders - increase in infections, extended healing time, scar tissue.
Chronic Progressive Lymphedema (CPL) - a debilitating, systemic disease of the lymphatic system in which the buildup of lymph fluid in the lower legs results in progressive swelling, with associated skin folds and lesions due to poor lymphatic drainage. Most often observed in draft breeds.
Conclusion
In general, maintaining good health practices such as regular exercise, proper nutrition, and hygiene can help to support a horse's lymphatic system and reduce the risk of developing lymphatic system-related health issues. It is also important to seek veterinary care promptly if a horse shows signs of lymphatic system problems.
Want to know more about how you can help support your horse’s lymphatic system? Give us a call! We will listen to you, help you make sense of your horse’s condition, and make recommendations to the best of our ability.
G’s Hedgerow contains 6 natural plant-based ingredients that support a healthy lymphatic system. Give us a call! We’d love to discuss how Hedgerow might be a great supplement for your horse!
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