The presence of a fever ring provides the farrier with a hint of what is happening internally within the hoof. In this laminitis case, increased growth on the lateral side of the right front foot indicates that the mare might have medial rotation of her distal phalanx. In the more traditional dorso-palmar rotational laminitis, the fever ring is wider at the heel than at the toe
Q: Are Fever And Stress Rings Due to Nutritional Changes?
If mild rings are present on all four feet, they are probably related to nutritional changes. The hoof is a complex, sensitive structure that responds to changes in a horse’s environment, health and nutrition.
The keratinized surface of the hoof wall consists of vertical growing tubules that form at the coronary band and grow down to the ground. The laminae and the soft tissues that the tubules suspend inside the hoof wall contain a web of blood vessels that provide nourishment to the hoof. In addition, they provide moisture and an entrance pathway for inflammatory cells.
Fever Ring Concerns
Fever rings may be formed as a result of laminar hyperplasia (thickening and/or excess growth), which can be induced by inflammation that displaces the tubules outward. A ring may also develop as a result of the tubules buckling of under compression. Typically occurring in the moist area near the coronary band, this is often a result of a sudden increase in weight or weight bearing (possibly due to lameness in another limb).
When a hoof or limb is injured, the inflammation that occurs may result in laminar hyperplasia. When there is systemic inflammation — such as often seen with episodes of colic, systemic illnesses, sepsis and hypersensitivity reactions — a ring may develop.
Nutrition may also be reflected in the hoof wall as nutrients help regulate hoof growth. Sudden changes in the diet can affect the environment within the gastrointestinal tract by encouraging some bacteria to grow while inhibiting the growth of others. A change in the horse’s gut environment may cause an episode of systemic change that incites laminar hyperplasia and/or a change in hoof growth rate, resulting in the formation of raised rings in the hoof wall.
If a sudden change in diet also brings a sudden increase in the horse’s body weight, buckling of the tubules may contribute to the development of these rings.
A ring in just one hoof is likely the result of a change only in that one limb and likely is due to an injury.
Finding a ring in all four feet is likely due to a systemic change or inflammatory response. The duration of the inflammatory response or buckling of the tubules determines the vertical measurement of the ring (how thick it is from top to bottom).
Since it typically takes a normal hoof on a healthy horse about 1 year to grow from coronary band to the ground, the approximate time of a change in the horse’s life may be estimated by the location of the ring along the hoof wall. For example, a ring that is mid-way down the toe of the wall indicates that the horse experienced an injury or other sudden change approximately 6 months earlier.
This horse had a systemic fever for several days 5 months ago and the ring is about 5/12ths of the way down the hoof. The horse has a marked fever ring that can be seen on the hoof as well as on the radiograph, which supports a theory that the horse developed laminitis and white line disease post-systemic infection. A nutritional change would be less deep in the foot and be present in all four feet. Fever rings can serve as a truth serum when you look at all four feet and need to determine the validity of the history that an owner is providing.
Attempting to blame one aspect of a horse’s environment or diet for all fever rings is inappropriate with the myriad of potential causes.
Though overall nutrition may play a role in the development of fever rings, sudden changes are typically the culprit. Certainly over time, nutrition plays a major role in the development of laminitis, which can produce some large fever rings.
That being said, the best way to reduce the occurrence of fever rings is to prevent injuries and maintain consistency in environment, diet and husbandry.
Floyd, Andrea and Richard Mansmann (2007). Equine Podiatry. Elsevier Saunders: Philadelphia, PA. pp 68-69.
Ross, Mike W. and Sue J. Dyson (2003). Diagnosis and Management of Lameness in the Horse. W.B. Saunders: Philadelphia, PA. p 242.