Page 156 - February_2023

VETERINARY VIEWS
We now know that basing maturity on growth plate closure is inappropriate to determine how to train a horse for athletic longevity.
GROWTH PLATES
Historically, people have measured a horse’s skeletal maturity by evaluating the time of closure of the growth plates. This technique has slight relevance to a racehorse that is started in intense racing as a two year old. The growth plates of the knees and hocks are well closed by 1-1/2 years of age, two years at the latest.
One critical feature of growth plates relates to conformational crookedness of the limbs, known as angular limb deformities. If a horse is toed-in or toed-out from the fetlock, surgical correction must be accomplished before he is two months old.
For angular rotations based around the knees or hocks, surgical correction should be implemented no later than 5 – 6 months to achieve reasonable success. Growth plates finish their development at very early ages, long before you’d consider a horse is mature enough to be ridden under saddle. A horse with a conformational imperfection, such
as a crooked leg, needs more time and diligence
in developing his musculoskeletal system with training. The objective is to strengthen the support structures in his legs to minimize rotational and twisting forces on a crooked limb.
Conditioning strategies have evolved through scientific application and understanding
of exercise physiology that has advanced considerably in recent decades. We now know
ADAPTIVE CHANGES IN RESPONSE TO EXERCISE
Loading of the limbs through exercise (dynamic loading) stimulates adaptive responses in long bones and in joint cartilage; these responses are critical to protecting joints from incurring too much impact stress under reasonable athletic conditions. Confinement of a young horse leads to varying degrees of disuse atrophy in all portions of the body,
but especially reduces the thickness of joint cartilage. Thinned cartilage is more at risk of injury.
The largest adaptations of joint tissues to limb loading occur within the first five months of life. These young, developmental adaptations continue through at least 18 months of age, at which point the tissues, particularly joints and tendons, behave more like that of a mature horse, with less malleable adaptations to exercise. Similar adaptive changes occur in exercised tendon and ligament tissue, which respond favorably to mild to moderate daily exercise. These soft tissues maintain their elasticity and rebound abilities when loaded and also improve in fiber alignment and orientation to impart tissue strength. Withholding exercise in the first months and years most certainly predisposes a horse to a myriad of joint or
provides him with the experience and agility that is later transferred to future athletic activities, while also stimulating adaptive protective responses in all his musculoskeletal tissues.
that basing maturity on growth plate closure is inappropriate to determine how to train a horse for athletic longevity.
tendon issues later in a horse’s athletic life. The early years during which a young horse learns how to use his body in pasture turn out
Confinement of a young horse leads to varying degrees of disuse atrophy in all portions of the body and especially reduces the thickness of joint cartilage.
154 SPEEDHORSE February 2023