The Space Between: Decoding Epiphysitis in Foals
When a foal hits the ground, it starts to grow. This is clearly a good thing. Unfortunately, in larger horse types which are bred for size (and the athletic ability that accompanies large stature), the astonishing rate at which young horses grow can cause problems.
By 6 months of age the foal will reach 80% of its adult height. Between 6 months and 1 year it only adds another 10%. So, from birth to 6 months the foal grows at a rate that is unique in domesticated animals. It is not surprising therefore that this growth has pitfalls for the health of the horse.
The most common problem encountered in these foals is epiphysitis. This word describes a condition where the ends of the longer bones of the foal become swollen and painful. The ends of the bones are called the epiphyses, and itis means inflammation = epiphysitis.
The foal grows by increasing the length of the longer bones of the legs – primarily the bones from the elbow and stifle downwards. These grow by laying down calcium into the fast-growing cartilage at the ends of the bones, close to the joints. This band of rapidly forming bone is called the epiphysis and is softer and less mature than other areas of the long bones.
What causes epiphysitis in foals?
In fast-growing, heavy foals, usually between 3 and 6 months of age, the weight of the animal can become too much for this ‘tender’ area of bone to support. The cartilage/young bone at these areas is crushed by excessive weight-bearing and becomes damaged and inflamed. This is seen as painful swellings just above the joints. The knee and fetlock are by far the most common joints affected as the front legs support 65% of the horse’s weight. These foals will of course have varying degrees of lameness.
Importance of nutrition and excercise
Clearly, nutrition of the foal will have an impact on epiphysitis. Foals fed a high calorie diet to encourage growth are much more likely to be affected than one allowed to grow at a steadier rate. As strong bones require adequate minerals in the diet, any deficiency or imbalance can exacerbate the problem. Correct Calcium and Phosphorous levels are vital, with Zinc and Copper also important.
Exercise is an important factor in helping growing bones to mature. The load bearing of the bones experienced in running around after the mare, or with other foals, encourages strong bone development. If the ground is dry and hard however, the concussion experienced through the immature bones will make epiphysitis more likely.
Thankfully, epiphysitis is rarely serious and will resolve in most foals if sensible measures are taken.
These will include.
- Reduce calorie intake so growth rate slows to a sustainable level.
- Restrict exercise, foal housed on soft surface in a smaller stall or paddock.
- Ensure mineral intake is optimal.
- Anti-inflammatory drugs may be used by veterinarians to reduce pain and swelling.
Epihysisitis could be seen as an example of what is referred to in farm animal veterinary medicine as a ‘production disease’. These are conditions which are caused, at least in part, by management factors and the drive for performance and growth. The most desirable and saleable foals in many horse sports are the ones which exhibit maximum growth and size at a young age. We must remember however that this does not come without risks to the juvenile skeleton. In this as in life, there is no such thing as a free lunch.
John Henderson, BVM&S MRCVS
