Na-L-ascorbyl-2-monophosphate as a source of vitamin C for channel catfish

Abstract

Channel catfish ( Ictalurus punctatus) fingerlings (1.5 g average initial weight) were fed semipurified diets supplemented with 0, 15, 30, 60 or 120 mg/kg (0, 0.08, 0.16, 0.32, and 0.64 mmol/kg) of ascorbic acid molar equivalent supplied by either Na-L-ascorbyl-2-monophosphate (AAP-Na) or Mg-L-ascorbyl-2-monophosphate (AAP-Mg). After 12 weeks, weight gain was significantly equal for all fish fed AAP-Na or AAP-Mg, although growth rate was less for fish fed the ascorbic acid-free diet (basal). There were no gross signs of vitamin C deficiency in any of the fish fed AAP-Na or AAP-Mg, while spinal deformities were found in 26% of the fish fed the basal diet. Bone collagen content was equal for all treatments with AAP-Na or AAP-Mg; however, there was reduced bone collagen content, a sensitive indicator of vitamin C deficiency, in fish fed the basal diet. Percentage recovery of ascorbic acid from commercially extruded catfish feeds supplemented with AAP-Na and AAP-Mg was 99 (±11.1) and 98 (±12.1), respectively. This study indicates that AAP-Na has equimolar activity to AAP-Mg as an ascorbic acid source for growth and collagen synthesis in channel catfish and that both compounds are highly stable against processing loss. Previous studies had shown that AAP-Mg has equal vitamin potency for channel catfish as L-ascorbic acid.