Dietary Protein Requirement of Juvenile Dianchi Golden-line Barbell, Sinocyclocheilus grahami

A 10-wk feeding trial was conducted to estimate the dietary protein requirements of juvenile Dianchi golden-line barbell, Sinocyclocheilus grahami (initial average weight 7.55 g). Five isocaloric diets were formulated to contain graded levels of protein (29, 34, 39, 44, and 49%). Each diet was fed to triplicate groups of fish in a recirculating rearing system maintained at 18-22 C. Feed intake of fish fed the diet with 39% protein was significantly higher than those fed the diet with 29, 34, and 49% protein (P<0.05). Weight gain, specific growth rate (SGR), and protein gain significantly increased with increasing dietary protein levels up to 39% (P<0.05), whereas no significant differences were observed among fish fed the diet with 39, 44, and 49% protein (P>0.05). In contrast, feed conversion ratio was significantly decreased with increasing dietary protein levels up to 39%. Maximum protein retention and protein efficiency ratio were observed in fish fed the diet with 39% protein. The regression analysis based on SGR and protein gain showed that the dietary protein requirements of juvenile S. grahami were 38.57% or 41.09% (equivalent to ca. 32.94% or 35.42% estimated digestible protein) of diet with a calculated digestible energy of 3.6 kcal/g.