Sunflower meal as a partial substitute in juvenile sharpsnout sea bream (Diplodus puntazzo) diets: Amino acid retention, gut and liver histology

The suitability of sunflower meal (SFM) as a substitute for fish meal was evaluated in sharpsnout sea bream fingerlings (14 g) by feeding diets in which 0, 10, 20 or 30% of crude protein provided by fish meal was substituted with SFM. The experiment lasted 125 days and survival at the end of the experiment was 95%. The effect of SFM level on growth parameters were not significant (P < 0.05). Fish were hand-fed to apparent satiation and feed intake ratio was not affected by SFM inclusion in the diet. Final live weight was 100 g for all fish fed all diets. Nutritional and biometric parameters were not affected by SFM substitution, but in body composition fish fed the diet with 20% of crude protein replaced by SFM substitution showed the lowest crude lipid level and the highest moisture content. Crude protein efficiency, gross energy efficiency and amino acid composition and retention of fish fed the various diets did not reach statistical differences. No histological alteration were found in liver, but an increment in goblet cells was observed in mucosa folds, perhaps as a consequence of SFM substitution or due to the high content of arginine and aspartate, known to be responsible for some immune responses. The results of this experiment demonstrated that SFM can supply up to 30% of crude protein in diets for feeding sharpsnout sea bream juveniles without any adverse effect on fish growth, liver and gut histology and amino acid composition and retention.