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Heteropneustes fossilis is found in most of the Asian countries and has high consumer demand due to its recuperative and medicinal qualities. Being a lean fish with high iron content, it is recommended to people suffering from anemia and cardiac diseases. In view of the above, two 8-week feeding trials were conducted to determine total sulfur amino acid requirement (TSAA) and cystine replacement value for fingerling Singhi, H. fossilis. In experiment I, six casein gelatin based isonitrogenous (380gkg−1 CP) and isocaloric (17.9MJkg−1 GE; 15.3MJkg−1 DE) amino acid test diets with graded levels of methionine (6.5, 8, 9.5, 11, 12.5, and 14gkg−1 of the dry diet) were prepared. Cystine was maintained at 4gkg−1 in all the diets. The diets were fed to quadruplicate groups of randomly assigned fingerlings (6.9±0.1g; 10.9±0.2cm) to apparent satiety twice daily at 28°C water temperature in a flow-through system (1–1.5Lmin−1). Based on the quadratic regression analysis at 95% maximum and minimum response of absolute weight gain (AWG gfish−1), feed conversion ratio (FCR), protein deposition efficiency (PDE%), energy deposition efficiency (EDE%), RNA:DNA ratio and methionine retention efficiency (MRE%), methionine requirements were found to range between 10.3 and 10.7gkg−1 of dry diet, corresponding to 27.1–28.2gkg−1 of the dietary protein. Hence, TSAA requirement was found to be 14.7gkg−1 of the dry diet (10.7gkg−1 methionine+4gkg−1 cystine). To find out the cystine replacement value for methionine, six diets with various ratios of methionine:cystine (90:10, 80:20, 70:30, 60:40, 50:50, and 40:60) on equimolar sulfur basis as per the TSAA requirement determined in experiment I (14.7gkg−1) were prepared and fed to fingerling H. fossilis (7.2±0.2g; 11.3±0.1cm) under identical laboratory conditions. The quadratic regression analysis of AWG gfish−1, FCR, PDE%, EDE%, RNA:DNA ratio and MRE% at 95% maximum and minimum quadratic response projected that cystine could replace from 39.6 to 40.2% of methionine requirement on an equimolar sulfur basis without hampering growth. On the basis of the above results, the total sulfur amino acid requirement of the H. fossilis is recommended to be 14.7gkg−1 dry diet (7.1gkg−1 methionine+7.6gkg−1 cystine) of which 39.9% was spared by cystine. [ABSTRACT FROM AUTHOR]

Abstract: Heteropneustes fossilis is distributed in most of the Southeast Asian countries. It is a promising species for aquaculture due to its high protein and iron content, ability to withstand shifts in salinity and temperature, and survival in oxygen depleted water. In view of the above, this study was undertaken to evaluate the effects of varying levels of dietary l-histidine on growth, protein gain, histidine retention, hematological and body composition of this fish so as to optimize the inclusion of histidine in its commercial feeds. Casein-gelatin based isonitrogenous (380gkg−1 CP) and isocaloric (17.9MJkg−1 GE; 15.3MJkg−1 DE) amino acid diets with six different l-histidine levels (5.0, H1; 6.5, H2; 8.0, H3; 9.5, H4; 11.0, H5; 12.5gkg−1dry diet H6) were fed to quadruplicate groups of fingerling Singhi (6.6±0.2g) twice daily at 07:00 and 17:30h to apparent satiation for 8week. Feeding trial was conducted in a flow-through system (1–1.5Lmin−1) at 28°C water temperature. Growth, feed conversion, protein gain and histidine retention of fingerling Singhi were found to increase significantly with the quantitative increase in dietary histidine from 5.0 (H1) to 9.5gkg−1 diet (H4). Hepatosomatic index, condition factor, hematocrit and hemoglobin were significantly affected in fingerling Singhi fed different concentrations of histidine and were also found to be best in fish fed diet H4. Quadratic regression analysis of the above parameters at 95% maximum and minimum plateau indicated that inclusion of histidine at 9.4gkg−1 of the dry diet, corresponding to 24.8gkg−1 dietary protein is optimum in formulating histidine-balanced, cost-effective, commercial feeds for intensive culture of Singhi. [Copyright &y& Elsevier]