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.