Effects of dietary marine sulphated polysaccharides (Algimun®) on growth performance, immune responses and disease resistance of juvenile gilthead seabream (Sparus aurata) to Photobacterium damselae subsp. piscicida

The present study evaluated the effects of a dietary mix of marine sulphated polysaccharides, named Algimun (R) (AL), supplementation to gilthead seabream (Sparus aurata) juveniles in terms of growth performance, immune responses, and resistance against Photobacterium damselae subsp. piscicida. A total of 240 fish (initial mean weight of 6.00 +/- 0.03 g) was randomly separated into 12 tanks (400 L, 20 fish per tank) distributed in four replicates. Fish were fed three experimental diets: a basal diet (Control), and a basal diet with two inclusion rates of Algimun (R) as 3 g/kg (AL0.3) and 5 g/kg (AL0.5) for 30 days before bacterial infection with P. damselae subsp. piscicida. After a 30-day feeding-period, growth performance was significantly improved in AL0.3 and AL0.5 groups compared to the control group (P < 0.05). AL0.3 and AL0.5 groups showed significantly higher lysozyme activity and myelopemxidase activity when compared to the control group (P < 0.05). The gene expression of immune mediators (IL-1 beta, IL-6, IL-10, IL-18, TNF-alpha and COX-2) was significantly upregulated in the intestine, spleen and head kidney in AL0.3 and AL0.5 groups when compared to the control group (P < 0.05). Eight days post-challenge, the survival rate against P. damselae subsp. piscicida was numerically higher in fish within AL0.3 and AL0.5 groups compared to control (+20%). The study findings suggest that marine sulphated polysaccharides (Algimun (R)) could be used as an immunomodulator in gilthead seabream to support animal's health and boost resistance in case of disease outbreak.

Automated summary

This study evaluated the effects of Algimun(R) dietary supplement on the growth performance, immune responses, and disease resistance of gilthead seabream juveniles. The results showed that the inclusion of Algimun(R) significantly improved growth performance, increased lysozyme and myeloperoxidase activity, and upregulated the expression of immune-related genes in the intestines, spleen, and head kidneys. Furthermore, fish fed with Algimun(R) exhibited higher survival rates against bacterial infection.