Evaluation of L-ascorbyl-2-polyphosphate (AsPP) as a dietary ascorbic acid source for channel catfish

Abstract

Channel catfish (Ictalurus punctatus) fingerlings were fed purified diets containing 0 or 100 mg/kg of ascorbic acid equivalent supplied either by ethylcellulose-coated ascorbic acid, ascorbate-2-sulfate, or L-ascorbyl-2-polyphosphate (AsPP). Fish fed the ascorbate-free diet exhibited external signs of scurvy at 11 weeks. Carcass ascorbate concentrations, histopathology of gill tissue, and radiographs evaluated at the end of the experimental period confirmed that fish fed the ascorbate-free diet were scorbutic. Signs of ascorbate deficiency were not observed in fish fed other diets. Weight gain and carcass ascorbate concentration were highest in fish fed AsPP. Improvement in weight gain and increased tissue concentration of ascorbate in fish fed AsPP is not readily explained, but may related to the resistance of AsPP to oxidation; thus providing a higher concentration of ascorbic acid at absorption sites. The data from the present study demonstrate the efficacy of AsPP in promoting growth and preventing scurvy in catfish.