Cattle are able to store considerable amounts of vitamin A in their liver and, to some extent, other tissues when they receive a liberal supply. Typically, animals with adequate liver stores need to be on a vitamin A deficient diet for several weeks or months before deficiency symptoms are observed.
Forage with dark green color will usually have high vitamin A content. Vitamin A content of stored forage will oxidize with time, so 1 year-old and older hay may need to be supplemented with Vitamin A.
