Abstract:

Vitamin C, or ascorbic acid (AA), is important in growth and physiological functions of fish. Six soybean meal-based (SBM) diets containing 0, 125, 250, 500, 1000 and 2000 mg.kg^-1 of AA were fed to snakehead, Channa striata (Bloch 1793) (initial weight 6.63 + 0.16 g) for 8 weeks in the laboratory. Survival of snakehead in the 250 and 500 mg.kg^-1 treatments was significantly higher  than the control, but not in the other treatments. Final weight and specific growth rate (SGR) of fish in all the AA-supplemented diet treatments were significantly higher (P < 0.05) than the control. Feed intake (FI), feed conversion ratio (FCR), and protein efficiency ratio (PER) also differed significantly, but not in a clearly dose-dependent manner. The requirement of AA for snakehead was calculated to be 277 mg.kg^-1. No vertebral anomalies were observed. Erythrocyte count was significantly (P < 0.05) higher at 1000 and 2000 mg.kg^-1 than at 0 and 125 mg.kg^-1. Fish in 250 mg.kg^-1 had significantly (P < 0.05) higher leukocyte count than those in 0, 1000, and 2000 mg.kg^-1. A bacterial challenge test with Aeromonas hydrophila revealed that 500 and 1000 mg.kg-1 had the lowest cumulative mortality. In an on-farm trial, SBM-based and commercial diets augmented with 0, 500, 750, or 1000 mg.kg^-1 AA were fed to C. striata for 23 weeks. All AA-supplemented SBM-based diets provided significantly (P < 0.05) higher final weights and overall yield than did all the AA-supplemented commercial diets. Maximum survival (85.3 %), final fish weight (573.5 g), yield (293.3 kg.hapa^-1) and profit (0.38 USD.kg fish^-1), as well as minimum FCR (1.16), production cost (1.12 USD.kg fish^-1) and feed cost (0.98 USD.kg fish^-1) were obtained with the 500 mg.kg^-1 SBM diet.

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Date 2018/09/30

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