As insoluble fiber content increases digestibility decreases. As hay maturity increases lignin and insoluble fiber content increases decreasing the hay's overall digestibility. Fats are becoming increasingly important in the horse's diet. Rancidity destroys fatty acids, fat-soluble vitamin and B vitamin absorption decrease, and palatability declines. Essential fatty acid deficiency, although rare, leads to a dull, dry hair coat, hair loss, and persistent infections.
Minerals give the body skeletal structures and serves in all body functions.
Microminerals are generally involved in enzymatic processes. Absorption of a mineral as a percentage decreases as its content in the diet increases. Other minerals may also be lost in the process. The only minerals generally of significance are Ca, P, NA, CI, Se, plus Cu and Zn for growth.