RELATIVE BIOAVAILABILITY OF L-ASCORBYL-2-POLYPHOSPHATE IN BROILER-CHICKENS

Broiler chick diets and drinking water were supplemented with two sour ces of vitamin C: crystalline L-ascorbic acid (AsA) or L-ascorbyl-2-po lyphosphate (APP) to provide 0, 25, 50, 100, 200, 400, 800, 1,600, and 3,200 ppm (mg/kg) AsA. The bioavailability of APP relative to AsA, as estimated by the change in plasma AsA concentration, was evaluated du ring 24-h periods of supplementation. When provided in the feed, no di fferences in dietary AsA content were attributed to vitamin source. In contrast, APP administration at 25 and 50 ppm, resulted in higher (P < .001) AsA values in drinking water when compared with AsA supplement ation. Plasma AsA values were elevated (P < .05) above baseline when e ither AsA or APP were supplemented in the feed or water at a level of 400 ppm or greater. Plasma AsA concentrations, following supplementati on of the diets, were higher (P < .05) in AsA-treated (800 ppm) chicks when compared with APP-supplemented chicks. During water supplementat ion, AsA (800 ppm) and APP (3,200 ppm) administration resulted in high er plasma AsA values when compared with their alternate vitamin source . At all other levels of water supplementation, no differences in plas ma AsA were associated with vitamin source. The absence of a consisten t difference in plasma AsA, relative to vitamin source, suggests that the isolated differences observed may be due to chance. It was conclud ed that APP was of similar bioavailability to that of AsA, as estimate d by the ability to elevate plasma AsA concentrations in broiler chick s.