AN EVALUATION OF DIETARY RIBOFLAVIN SUPPLEMENTATION ON GROWTH-RATE, FEED-EFFICIENCY, RATION METABOLIZABLE ENERGY CONTENT, AND GLUTATHIONE-REDUCTASE ACTIVITY OF BROILERS

The nutritional adequacy of National Research Council dietary recommendations for riboflavin was evaluated in growing broilers. Treatments evaluated included: 1. a basal corn and soybean meal ration containing 2.6 ppm riboflavin; 2. as treatment 1 with riboflavin supplemented to National Research Council recommendations of 3.6 ppm riboflavin; 3. as treatment 2 plus 3.6 ppm riboflavin; and 4. as treatment 2 plus 14.4 ppm riboflavin. Live weight gain and survival were depressed (P<.05) by 8 and 5% at 4, but not at 8 weeks posthatching for treatment 1 as compared with treatment 2. Increasing riboflavin supplementation from National Research Council recommendations to 2 and 4 times the recommended level increased (P<.05) live weight gain by 5%, and nitrogen-corrected metabolizable energy by 7% at 8 weeks posthatching. Blood glutathione reductase activity and carcass parameters were not impacted by dietary riboflavin level. The data suggests that the National Research Council recommendation of 3.6 ppm dietary riboflavin for growing broilers is satisfactory through 4 weeks, but that benefits are obtained by exceeding the 3.6 ppm recommendation through 8 weeks.