Effect of hydrolysed fish protein and autolysed yeast as alternative nitrogen sources on gilthead sea bream (Sparus aurata) growth performances and gut morphology

The aim of the present study was to compare the effects of two different nitrogen-rich ingredients such as hydrolysed fish protein and autolysed yeast, on gilthead sea bream (Sparus aurata) growth performances and histological gut morphology. Animals were allocated to three experimental groups: the first received a fishmeal-based diet (FM), the second and the third received hydrolysed fish protein (HFP) and autolysed yeast (AY), respectively, to replace an equal amount of fishmeal. The experiment lasted 92 days. No significant differences in body weight and mortality were observed among the different groups. Villus branching, intraepithelial lymphocytes and inflammatory infiltrate of the submucosa were more prominent in AY than HFP and FM. The gut absorbent surface ratio was 5.94, 6.44 and 7.28 for group FM, HFP and AY, respectively, with statistical significant difference between FM and AY and between HFP and AY. A significant increment in the goblet cell density was observed for HFP and AY in comparison to FM. A statistically significant increase in small-sized goblet cells was observed in AY compared to FM. All our findings suggest that it is possible to use either HFP or AY, as partial replacer of FM in the S. aurata diet.Highlights Yeast-derived products as a suitable alternative nitrogen source. Autolyzed yeast as a novel approach in the use of yeast products. Use of autolysed yeast for replacing fishmeal in aqua feed. Use of hydrolysed fish protein for replacing fishmeal in aqua feed