#bone development

The potential consequences of starting a horse under saddle too young. “Today, more and more, the big money futurities for performance horses are for three-year-olds, so in order to be competitive, these horses MUST be started as two-year-olds, and sometimes even when they are long-yearlings (18-24 months old). Because of this, many of these horses end up with bowed tendons, Navicular Syndrome, bone spavins, bone chips, stifle injuries, blown-out hocks, hairline fractures, arthritis, severe back problems, sprained necks and a myriad of other problems and conditions associated with stress and strain to young, developing bodies. Many horses will end up with debilitating problems at only four or five-years-old and already receiving anti-inflammatory medications and/or painkillers on a daily basis in their feed, or in the form of injections. Some older horses, in their teens, will develop problems that can be traced directly back to being started too young and too hard. It will take 10 or so years for the stresses they experienced when younger to appear as problematic

Even at two and a half years old a horse is still just a teenager. He’s not physically mature, nor will he be completely mature, until he’s at least six. In spite of what many in the horse industry believe, all horses regardless of breed mature skeletally at the same rate. Even the most conscientious of horse owner concentrate their concern on a horse’s developing legs, but growth plates are not just in a horse’s knee. There is a growth plate on either end of every bone starting behind the skull, and continuing throughout the remaining skeletal areas. In the case of some bones like the pelvis there are multiple growth plates. Taking the age of final maturity which ranges between 4 – 6 years of age into consideration, as well as the rate of bone fusion in the growth plates, ideally a horse shouldn’t be ridden and worked regularly until the minimal age of four. “

The Significance of Too Much Too Soon.

When trying to explain the justification and common sense of waiting until at least 3 years of age to introduce a horse to light work under saddle and incrementally increasing that workload over the next year to a competitive/ performance level by age four, I am almost always inevitably confronted with an impatient disapproving owners condescending response in notifying me that race horses have been started early for centuries and are already often competing at age two. 

All above information came from here 

Musculo-skeletal unsoundness, particularly related to bone failure and joint injury in racing, equestrian and other athletic horses, can be linked to overloading of bone structures relative to the body weight of the horse, the age at which the young horse is first worked, the speed of exercise and degree by which the bone and joint structures are able to adapt over time to additional body weight and loading forces (Ireland, 1998; Davies, 2001). After each period of exercise, even in growing horses, the bones remodel or react to increase strength, circumference and mineral density (collectively called bone mass) while internal trabecular structures adapt to withstand the increased loading forces. This is a relatively slow process, which can take up to four months to complete in a progressive remodeling process in the young horse exercising during the growth phase or in athletic training before maturity (Lawrence, 2003b).

Bone adaptation to exercise One of the earliest studies in America on Thoroughbred and Quarterhorse weanlings concluded that bone strengthens by increasing its mineral density, principally by depositing calcium within bones (Raub et al., 1989). These researchers found that over an 111-day period the cannon bones of weanlings exercised by trotting, initially over 400 meters and increasing to over 4 km per day, accumulated 25% more bone calcium than weanlings that had been stalled overnight and turned out into pens during the day. Numerous other studies, cited by Jeffcott (2001), Firth (2003a) and Lawrence (2003b) in a review of osteochondrosis and response to exercise in horses, have reported similar adaptive responses in foals and weanlings up to five months of age, with a lower bone density in the cortical shaft and subchondral bone mass in non-exercised compared to exercised young horses. After six months of identical exercise, the young horses in the original non-exercised group remodeled the bone, in this case the stifle joint, to establish an equal mineral density and cross-sectional area (Lawrence, 2003b).

(NOTE= Exercise =/= riding, as stated the horses can be lunged or exercised in hand)

It is important that young growing horses have access to free paddock exercise to encourage the formation of sound cartilage and subchondral bone, while over-exercise and excessive weight loading in heavy weight young horses can result in damage to the developing joint cartilage and subchondral bone in joints (Firth, 2003a). Jeffcott (2001) and Firth (2003a) concluded that the effects of high energy:nutrient ratios, confinement to small yards and over-exercise or lack of adequate exercise, high weight loading and inadequate trace minerals and calcium balance, all adversely influence the cartilage development, bone mineralisation and maturation of the skeleton in the formative years of a horse’s life.

Avoid tight circle tracks Do not gallop young horses around tight, compacted curves or end circles on the track too early in their training preparation. Gallop only up straights initially, then work progressively faster into corners and around end circles to allow adaptation to the centrifugal sideways strain forces, starting after 6-8 weeks of training. Avoid sudden introduction to fast work and limit speed of galloping around unbanked, relatively tight bends initially, especially on dry, compacted tracks. (AKA don’t barrel race 2 year olds!)

Conclusion

The soundness of the skeletal structure in growing and exercising horses is largely dependent on providing an adequate diet with a balanced intake of bone and joint structural nutrients during the formative years of a horse’s life. Controlled exercise will assist in the skeletal development and allow remodeling in response to loading in both growing and exercising horses. Care when formulating feeds, premixes and supplements to ensure optimum bioavailability and stability of skeletal nutrients is essential to maintain long term athletic soundness in all classes of horses.

Came from this article 

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