Alternative plant protein sources in sea bass diets

Abstract

A control diet (C) containing animal protein (mainly fish meal) was compared with 6 experimental diets containing different 

plant proteins (soybean meal, SM; rapeseed meal, RM; potato protein concentrate, PPC and a mix of the three vegetable 

protein sources, M). The plant protein replaced either 25 (1) or 50 (2)% of the animal protein with the exception of diet 

RM2 where the substitution rate was lowered to 35%, and in diet M where 55% of the total protein given was replaced in 

equal amounts by the three plant proteins. For the growth trial, which lasted 97 days, 528 European sea bass (initial live 

weight 107 ± 0,06g), distributed among 24 fibreglass tanks with three replicates per treatment, were used. The pelleted 

feed was distributed 5 times per day using an automatic dispenser. Energy, crude protein and crude fat digestibility values 

for fish meal and soybean meal were similar and not statistically different while the values for rapeseed meal and potato 

protein concentrate were significantly lower. Digestive utilization for NFE was higher in fish meal and decreased significant- 

ly in soybean meal, rapeseed meal and even more noticeably in potato protein concentrate. Diet digestibility values showed 

a similar trend with a clear worsening effect at the higher inclusion rates used. Diet M gave digestibility coefficients lower 

than those observed with diets C, SM1, SM2, RS1and RS2and higher than those of diets PPC1and PPC2. Fish fed a diet in 

which 25% of the total protein was replaced by soybean had similar performances to those of the control group. On the 

other hand, sea bass fed diets SM2, RS1, RS2and M had lower growth rates and worse feed utilization than those observed 

with the control. Finally, specific growth rates and food conversion efficiency in sea bass fed diets containing potato protein 

concentrate were poor because of the low palatability. These results show that soybean meal can substitute up to 25% of 

the total protein of the diet without any negative effect on sea bass performance.