Riboflavin is one of the vitamins most likely to be deficient for swine. Riboflavin fortification levels should be adjusted, especially to offset the exclusion or reduced amounts of riboflavin-rich ingredients such as milk fermentation and fish by-products and dehydrated alfalfa from computerized least-cost swine formulations. Swine diets based on grains and plant protein sources are often borderline to deficient in riboflavin. Only a few feedstuffs fed to swine contain enough riboflavin to meet the requirements of growth and reproduction. As early as the 1950s (Briggs and Beeson, 1951), researchers realized that weanling pigs, when raised in drylot and fed an ideal combination of high-quality protein supplements in a grain ration fortified with essential minerals, vitamins (including B12) and an antibiotic, had improved growth and feed efficiency when three B vitamins (riboflavin, calcium pantothenate and niacin) were provided. Swine in confinement become more dependent on adequate vitamin (including riboflavin) and trace mineral supplementation, because least-cost feed formulation limits the number of vitamin-rich feed ingredients. The greater the variety of feed ingredients, the lower the chance of vitamin and trace element deficiencies for animals and humans alike (McDowell, 1989).
Riboflavin is remarkably stable during heat processing. However, considerable loss may occur if foods are exposed to light during cooking and some losses occur in feed administered to animals out of doors. Only that portion of riboflavin in the feed exposed to light would be destroyed, therefore this may be of little significance as only the top of concentrate mixtures in automatic feeders would be affected. In dry form, riboflavin is extremely resistant to oxidation even when heated in air for long periods. While it has been shown that 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 (Hoffmann-La Roche, 1969). Riboflavin is quite stable in multivitamin premixes (Frye, 1978).
