Effects of dietary amino acid l ‐lysine on survival, growth and haemato‐biochemical parameters in Indian catfish, Heteropneustes fossilis (Bloch, 1974), fingerlings

Summary An 8‐week feeding experiment was conducted to estimate the dietary lysine requirement of fingerling Indian catfish, Heteropneustes fossilis (total length = 6.35 ± 1.10 cm; weight = 4.70 ± 0.65 g) by feeding six isonitrogenous (400 g/kg CP ) and isocaloric diets (17.90 kJ/g) containing six supplemental lysine levels ranging from 11.0 to 23.5 g/kg (diets I to VI , in incremental steps of 2.5 g/kg). Triplicate groups with 20 fish each were stocked in 75‐L circular continuous flow‐through troughs and fed experimental diets at 4% BW /day twice daily (08:00 and 18:00 h). Maximum live weight gain (304%), best‐feed conversion ratio ( FCR , 1.46) and protein efficiency ratio ( PER , 1.71) were obtained at 18.5 g/kg dietary lysine, beyond which these values showed a slight declining tendency. Best values for somatic and hematological indices were also obtained at this level. Significantly ( p  <   .05) higher body protein and low carcass moisture and intermediate fat contents were noted in fish fed diets containing 18.5 g/kg lysine. The quadratic regression analyses of live weight gain, FCR , PER and body protein deposition (BPD) data indicated lysine requirements at 19.3, 18.8, 18.6 and 18.6 g/kg of dry diet, respectively. Based on these results, it is recommended that the H. fossilis diet should contain lysine at a level of 19.0 g/kg of dry diet, corresponding to 47.5 g/kg of dietary protein, for optimum growth and efficient feed utilization.