Dietary essentiality of ascorbic acid in rohu larvae: Quantification with ascorbic acid enriched zooplankton

Gopa Mitra, P.K. Mukhopadhyay-2003

Aquaculture International, 11 (1-2): 81-93

Abstract:

Carp larvae, like any other fish larvae depend on natural food during first few days of their life. In nursery conditions, high mortality and slow larval growth are of common occurrence; sub-optimal nutrition might be a possible reason for such consequences. To improve the situation the effect of feeding ascorbic acid-enriched live food on survival, growth, tissue biochemical composition including ascorbate level was evaluated in first feeding (3 days old) larvae (av. wt. 2.2 mg) of the rohu carp, Labeo rohita (Ham.) for a period of 15 days (temp. 28.6 ± 1 °C) under natural photoperiod. The larvae (stocking density 10 l^-1) were offered enriched and non-enriched zooplankton ad libitum following a rigid schedule with four feeding regimes, each having 3 replicates. In treatment T₁, non-enriched zooplankton (Moina, Daphnia, Cyclops, Diaptomus) and in T₂, T₃, T₄ ascorbic acid enriched (12 h enrichment) zooplankton [@10%, 20% and 30% ascorbyl palmitate (AP) inclusion in diet of zooplankton] were offered. Highest survival (90%) and growth (9563% live weight gain) could be seen in T₃ group and the lowest in T₁ (62% survival and 805% live weight gain), thus confirming the dietary essentiality of ascorbic acid for rohu larvae. The requirement has been shown to be 1409 µg/g dry diet. Whole body tissue analyses for crude protein, total lipid and RNA: DNA ratio followed the same trend as that of growth response and percent survival. Significant positive correlation (r = 0.949 and 0.861) could be found with muscle RNA/DNA ratio and muscle RNA content with specific growth rate in different treatments. Significant difference was found in tissue ascorbate levels between enriched plankton fed groups, being highest in T₃. Such live food mediated vitamin transfer might be an effective means to provide higher plane of nutrition for high survival and rapid growth for rohu larva.

(Nutrition & Biochemistry Division, Central Institute of Freshwater Aquaculture, Kausalyaganga, Bhubaneswar-751 002, India, e-mail: gopamitra@yahoo.com)

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