The effect of time-dependent protein restriction on growth factors, nonspecific immunity, body composition, fatty acids and amino acids in the Siberian sturgeon (Acipenser baerii)

The effect of time-dependent protein restriction (PR) and refeeding were investigated on growth, body composition, fatty acids (FA), amino acids (AA) and nonspecific immune functions in the juvenile Siberian sturgeon (Acipenser baeri; 75 +/- 5g). Test diets included: T1 (control) and T2 fish fed diets containing 400 and 300g/kg protein respectively during the whole experimental period, T3 (every other day) and T4 (every other week) fish were fed diets containing 300g/kg protein (PR) and refeeding with diet containing 400g/kg protein respectively, and T5 fish fed a diet containing 300g/kg protein for 3weeks and a diet containing 400g/kg protein for 5weeks, were fed to the fish for 56days by visual satiation. Unlike ration T2 and T5, feeding treatments of T3 and T4 showed an increase in fish growth and body composition (p<0.05) and they were very close to the control group (p>0.05). Regarding the fatty acid profile, although the percentage of highly unsaturated fatty acids (HUFA) and polyunsaturated fatty acids (PUFA) declined significantly in the T2 and T5 groups, the saturated fatty acid (SFA) and monounsaturated fatty acids (MUFA) indicated no change among the treatments. In addition, the T2 and T5 groups demonstrated a reduction in essential amino acids (EAA) with a simultaneous increase in nonessential amino acids (NEAAs), which was significant from that of controls and other groups (p<0.05). In terms of nonspecific immune parameters (serum lysozyme activity and alternate complement activity [ACH50]), treatment 3 has an appropriate result that did not have a significant difference with the control group (p>0.05), but there was significant difference with other groups (p<0.05). As a result, the T3 treatment can be used in sturgeon aquaculture practically without any negative impacts on biological or physiological indices.