Vitamin D
Vitamin D functions in the pig's body to increase the absorption of calcium and phosphorus from the intestines. It is necessary for good bone growth and calcification. Vitamin D2 sources include sun-cured hays, irradiated yeast and dehydrated alfalfa meal. Sources of D3 include fish-oils and fish meals and formation of D3 in the skin by sunshine. Swine exposed to sunshine in the summer should not need dietary vitamin D. During the winter months and in confinement rearing, it is important that rations be supplemented with vitamin D.