Effects of supplemental riboflavin in adult ruminants have not been well investigated. Osame et al. (1995) reported that intramuscular injection of riboflavin (10 mg per kg body weight in calves; 5 mg per kg in cows) increased blood neutrophil count and bactericidal activity one to six days after injection. Milk is an extremely rich source of riboflavin, and therefore young, nursing ruminants should receive ample supplies of the vitamin. Prior to full rumen development young ruminants require riboflavin. Milk replacer should be formulated to contain at least 6.5 mg per kg (3.0 mg per lb) of dry matter.
Riboflavin is remarkably stable during heat processing. However, due to its instability to light, considerable loss may occur in feeds exposed to light during processing. In dry form, riboflavin is extremely resistant to oxidation, even when heated for extended periods. Field-cured alfalfa hay exposed to moisture can lose a significant amount of its riboflavin content in a relatively short time. Under common circumstances, riboflavin has good stability when added to mixed feeds. Riboflavin is quite stable in multivitamin premixes (Frye, 1978). A recent report demonstrates a 99% retention of riboflavin after six months in a vitamin premix; however, the retention was only 59% when the premix contained choline and trace minerals (Gadient, 1986).
