Responses of yellow catfish (Pelteobagrus fulvidraco Richardson) to low-protein diets and subsequent recovery

A 4-week growth trial was conducted to investigate the effect of low-protein diets on the growth and amino acid (AA) composition of yellow catfish, and subsequent recovery when the fish were then switched back to the control diet for a further 4 weeks. Three isolipidic and isocaloric diets containing 390 g kg^-1 (Control), 320 g kg^-1 (D320) and 260 g kg^-1 (D260) graded protein levels were evaluated. During the protein restriction period, specific growth rate (SGR) of D320-and D260-treated fish was significantly reduced by 20.79% and 29.21% compared to the control fish, respectively (P < 0.05), while significant improvements in protein retention efficiencies were observed in fish fed with the D320 (12.82%) and D260 (19.58%) diets (P < 0.05). The D260-treated fish had significantly lower (0.87%) whole-body essential amino acid (EAA) and significantly higher (0.74%) non-essential amino aci (NEAA) concentrations compared to the control fish. After a 4-week realimentation, significant increases in the SGR of the protein-restricted fish were observed. However, no significant differences in the whole-body EAA or NEAA concentrations among groups were observed (P > 0.05). The results indicate that previously protein-restricted yellow catfish can compensate completely in terms of final body weight, growth rate and whole-body AA concentrations.