Physical activity is essential for growing youngsters of any species. In horses, exercise is key for healthy bone growth and the avoidance of developmental orthopedic disease. Stress, a product of body load (weight) and activity, dictates the size and number of mature bone cells a young horse produces. Because growth occurs rapidly in a foal, continual stress is needed to cause strong bone growth.
A stoppage of exercise due to illness of the mare or foal, or weather or management practices, can result in newly formed bone that’s inadequate. A few days won’t matter, but several weeks of confinement can leave your young horse with a significant amount of structurally inferior bone. Then, when exercise resumes, the now larger foal’s normal activity can turn stress into trauma on the poorly prepared bone.
So be sure to give your young horse as much daily turnout as possible. Also, check with your vet on how best to manage a return to exercise after any unavoidable periods of confinement.
Source: Kentucky Equine Research