Dietary Ascorbic Acid Requirements of Fingerlings of Genetically Improved Rohu (Labeo rohita Ham)

Abstract

Indian major carp, including Labeo rohita, are incapable of biosynthesizing ascorbic acid due to the absence of the enzyme L-gulono-γ-lactone oxidase. To assess their ascorbic acid require- ments, improved rohu fingerlings (2.33±0.18 g) were fed one of six semi-purified formulated diets containing 0, 20, 40, 60, 80, or 100 mg ascorbyl-2-polyphosphate (APP) per kg feed for 60 days in water of 28-30°C. Fish fed diets deficient in ascorbic acid had a significantly lower weight gain, poor feed conversion (FCR) and protein efficiency (PER) ratios, lower survival, and behavioral abnormalities such as lethargic movements and poor feed intake. The best FCR and PER were recorded in the 60 mg APP diet. Ascorbic acid in the kidney dropped from 36.62 to 5.09 mg/kg by the end of the experiment. Weight gain analysis by regression indicated that the dietary ascor- bic acid requirement for maximum growth and survival of rohu fingerlings can be achieved with 53.5 mg APP incorporated into 1 kg diet.