Why is it important to have a knowledge of a horse's skeletal maturity?
The framework of a horse’s body is its skeletal system, it protects the organs and without it, your horse would be a blob on the floor. Bones are restructured continually by living cells. For example, if you took a young horse and chased it round a track one-way several times a day for say six months and then analysed their cannon bones you would find that the inside track cannon bone would be denser and thicker. Therefore a bone maybe a non-living structure secreted by the body, but it is controlled and modelled for our horse’s needs in its environment.
There are several processes going on as a horse matures, growth plates producing cells so bones can reach their full height, bones fusing to each other, ossification of cartilage to bone, and thickening. These take place at varying stages until a horse is fully mature, however, a horse can improve bone density and repair itself throughout life. Bone in an embryo of a horse starts off as a collagen network of fibres the same stuff as a spider's web. This is secreted in the correct bone shape in a mesh-like pattern. Bone cells within the collagen network produce cartilage and it’s this cartilage that then forms bone. The process of turning cartilage to bone involves deconstruction of the cartilage and reconstruction of bone. When a horse is born all its bones are formed except for either end, which is still cartilage and these are known as growth plates. Bones like the vertebrae have multiple growth plates and the vertebral column will be one of the last set of bones to fuse in a horse and not before a horse is 5 ½. Different breeds of horses and ponies grow and mature at different rates and times, but no horse is mature before 5 ½ and most are 6 and over. This maturing also coincides with teeth eruption which is another clue to when a horse reaches maturity. The coffin bone fuses at birth and these fusions follow on up the leg. However, the coffin bone may not increase in height but it does carry on getting larger and wider. Where wings called the palmar processes start out as cartilage and forms the wings of the coffin bone and they do not fully develop until a horse is 5 years old. Therefore, there are several processes going on, even in the coffin bone as the horse matures. Horseshoes put on a horse before the age of 5 will manipulate the shape of their hooves and coffin bone. They basically change the shape of the horse’s hoof. This is why we have nearly all our domesticated horses with some form of contraction of the heels. If owners were aware of this it may make them think more carefully about shoeing their horse. This maturing is: growth until fusion, ossification of cartilage, and the thickening of bones. Every bone has a periosteum it maybe called something different in some bones and vets may argue, but every bone needs a periosteum to allow it to thicken and be able to repair itself. The lengthening/growth of bones through growth plates takes place at varying stages until a horse is fully mature. The bones below the knee and hock are fuse quite early in life, however, these bones carry on thickening until full maturity. The Femur fuses between 3 and 4 where the Pelvis does not stop growing until after the horse is 5. This also depends on breeds, sex and size where a 17 hand Warmblood gelding may not fully mature until they are nearly 8 years old.
Why is it important to have this knowledge? Understanding how a horse’s body matures will affect every aspect of equine care and training. It will allow owners and equine professionals to make informed decisions about horses under their care and most of these decisions have a fundamental effect on a horse’s well-being. Putting unnatural stresses and strains on a young horse’s body before it’s fully mature by training and competing them is not a good idea. However, exposing a young horse to different terrain and giving them an environment to increase bone density and mature as nature intended is. There is a balance all owners of young horses have to walk and that is between being too protective and doing too much too soon. Handling a horse from a very young age has been a part of good horsemanship for many years. Progressing this training on with groundwork and getting a horse use to equipment is an ongoing cycle of a modern domesticated horse’s development. The real question is when should we start riding our horses? And like the answer to most questions is, it depends. Not many owners or trainers do enough groundwork with their horses and mainly because of their own lack of knowledge they are often too eager to get on. The vertebrae fusing later in the process is significant because they contain many growth plates and the direction of force from a rider are opposed to that of the vertebral column. You can now see why structural damage to a young horse’s back is much more common than in its legs. Personally, I would not take any risks and would not start riding a horse until it is 6 years old and I would leave competitive training or competing in any discipline until that individual horse is fully mature.
Preconditioning young horses like in racing does not create stronger bones as many think. It only puts more stress on a young horse’s legs than designed. Training and riding young horses hard is not a good idea, however, exposing them to different terrain and giving them an environment to mature and increase bone density as nature intended is. If owners and equine professionals understood this maybe the paddock paradise system would be more popular.
A horse’s skeleton is not mature until the age of 5 1/2 and this also depends on breed, sex and size. How does this knowledge affect our thinking? It should affect everyone's thinking, but it will not for the majority of equine professionals who earn their living out of producing a young horse. There are too many welfare issues within the equine industries and this is yet another. Owners who put their horse’s first before their own interests will change with this knowledge, but racing and other equine breeders & trainers will not change unless there is public pressure for them to do so. Even then I cannot see the racing industry changing. I think the biggest problem would be actually them admitting that they are wrong training and competing horses so young. Also, the money involved in racing dictates their thinking. Recently a world top trainer based in the UK was charged with giving horses anabolic steroids, all the classics are for 3-year-old horses and he needed a more mature horse at an early age, you can see why their greed gets the better of them when you consider the winner of the English Derby receives well over ¾ of a million pounds and stud values are increased astronomically for a prestigious classic winner.