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.
Fat Soluble Vitamins. Among the fat soluble vitamins, Vitamin A helps form and maintain healthy body tissues while vitamin D helps the body absorb calcium. Vitamin E is important for red blood cell formation and absorption of vitamin K, which is important for blood clotting.