I.U. 500 Vitamin E Thou. 200 Vitamin sources and general comments Vitamin needs of swine are met either from that contained in the feed or from synthesis in the body of the animal. Determinations have been made of the vitamin content of many swine feeds. These are average figures and, in some cases, are influenced drastically by the method of harvesting, processing and storing. Vitamin A does not occur in plant products but the plant pigment carotene can be converted to vitamin A in the intestinal wall of the pig.
Yellow corn is the only cereal grain that contains significant amounts of carotene.
Forages are good sources of carotene, but they are seldom used in today's practical rations. One milligram of B-carotene is equivalent to 500 I.U. of biologically active vitamin A for the pig. Storage and exposure to air. Exposure to light and high temperature. Exposure to metals such as iron hasten destruction.