Riboflavin is one of the vitamins most likely to be deficient for poultry. Riboflavin fortification levels should be adjusted, especially to offset the reduction or exclusion of riboflavin-rich ingredients such as milk fermentation and fish by-products and dehydrated alfalfa from computerized least-cost poultry formulations. Poultry diets based on grains and plant protein sources are often borderline to deficient in riboflavin. Only a few feedstuffs fed to poultry contain enough riboflavin to contribute to the requirements for growth and reproduction. Poultry in confinement become more dependent on adequate vitamin (including riboflavin) and trace mineral supplementation as least-cost feed formulation (i.e., using principally corn and soybean meal) limits the number of riboflavin-rich feed ingredients (such as milk by-products, fermentation products, fish by-products and dehydrated alfalfa). The greater the variety of feed ingredients, the lower the chance of vitamin and trace element deficiencies for animals and humans alike.
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 diets fed to animals out of doors. Only the portion of the feed exposed to light would be destroyed, therefore this may be of little significance as only the top layer 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 normal circumstances riboflavin has good stability when added to mixed feeds (Hoffmann-La Roche, 1969). Riboflavin is quite stable in multivitamin premixes (Frye, 1978).
Naber and Squires (1993a) reported that the average albumen riboflavin content of eggs determined in their random survey was 4.05 µg per g. The efficiency of transferring riboflavin from the diet to whole egg declined with increasing dietary levels of supplemental riboflavin. However, the transfer appeared to be 46% efficient when diets were supplemented with up to 4.4 mg per kg (2.0 mg per lb) of riboflavin. Thus the potential to fortify eggs with riboflavin appears high. Squires and Naber (1993a) noted depressed levels of both yolk and albumen levels of riboflavin if the diet was supplemented with less than 4.4 mg per kg (2.0 mg per lb) of the vitamin. In breeding hens, low albumen riboflavin content had an immediate effect on embryonic development and, ultimately, hatchability of fertile eggs. Therefore, for both commercial and breeding Leghorn hens, it was determined that supplementation of riboflavin should be no lower than 4.4 mg per kg (2.0 mg per lb). Based on these data, it may be speculated that the fortification needs of broiler breeders and turkey breeders would be much higher than this level reported for Leghorn hens.
Cook (1992) reported significant performance improvements in turkeys when riboflavin and (or) thiamin were increased to levels that exceed current industry averages. Similarly, the riboflavin requirement for broilers was reported to be higher than the industry average used today (Teeter and Deyhim, 1993). Some commercial turkey operations have adopted the practice of feeding higher levels of riboflavin (also vitamins C and E) to protect against a pale, soft, and exudative syndrome (PSE) in meat.
There is controversy on the concept of removing vitamins and trace mineral supplementation from poultry and other species' diets some time prior to slaughter. Skinner et al. (1992) reported that removal of vitamins and trace minerals from broiler diets did not impact performance. However, Teeter and Deyhim (1993) detected reduced performance and carcass variables when the same period was examined. Teeter and Deyhim (1996) reported reduced performance, carcass variables and increased mortality for both poultry and swine receiving inadequate vitamin supplementation. Deyhim et al. (1996) withdrew vitamins and trace minerals for 21 days in broiler diets during heat stress and found 37% less riboflavin in the Pectoralis major muscles. Such effects have the potential to impact consumer perception of poultry meat as wholesome and should be considered when vitamin withdrawal is being contemplated.
