Ok-so I've been riding for 40 years, and teaching and training for 20. I have always based a horses' jump on his athletic abilities, scopiness, etc. I've seen the solid, 2'6 packers that can stretch to 3' but are better suited to the 2'6 job.
Bioactive vitamin D or calcitriol is a steroid hormone that has long been known for its important role in regulating body levels of calcium and phosphorus, and in mineralization of bone.
Vitamin A. Every cell in your body needs vitamin A. This nutrient regulates the growth and division of your cells and it helps your body produce white blood cells when you need to fight an illness or infection. It plays a role in remodeling bone and it keeps the cells that line your body's interior surfaces healthy.