Abstract
The fast growing modern-day aquaculture presents many challenges in the aspect of the fish health and nutrition. Overabundance and overuse of antibiotics raises concerns regarding bacterial resistance, residues, and environmental toxicity, and warrants the need for the alternative approaches.1,2 Various nutraceuticals are currently being evaluated as safe and cost-effective prophylactic supplements and/or growth promotors in fish diets.3,4 IMUNO-2865® is a commercially available, β–glucan based, natural hemicellulose compound with proven immunostimulative properties in people, domestic and some aquatic animals.5,6 This report presents a compilation of all the recent studies that were investigating IMUNO-2865® as a dietary supplement in the commercial aquaculture for sea bream (Sparus aurata, Linnaeus, 1758) and in experimental freshwater conditions for juvenile chub (Squalius cephalus, Linnaeus, 1758), conducted in 2 separate trials.
Experimental feeding trial with IMUNO-2865® supplementation in juvenile wild-caught chub under laboratory freshwater conditions resulted in overall higher growth performance for all experimental groups regardless of the concentration of the added compound. The maximum, 5% concertation of the supplement, resulted in highest weight gain and calculated specific growth rate. Measurements of the malondialdehyde (MDA) concentration as a lipid peroxidation marker was used to assess the level of the oxidative stress in the muscle. These results were highly variable and not statistically significant (P>0.05), although the 1% supplementation showed the lowest MDA levels.7
A summary of cellular and biochemical blood parameters, and oxidative stress responses in gilthead sea bream under winter stress conditions on a commercial farm showed some favorable effects.8,9 No mortality was observed throughout the experiment. Variability among various blood parameters was noted throughout the study and no statistically significant differences were noted among treatment groups for a total number of erythrocytes, leukocytes, basophils, eosinophils, lymphocytes and thrombocytes. However, significant increases in numbers of monocytes and heterophils were observed in the group supplemented with 2.5 % of IMUNO-2865® in the feed (Group 4). An overall increase of erythrocytes was noted by the end of the experiment, although with variable distribution among groups. Blood Ca++ levels, total proteins, and total NH3, were significantly higher after 60 days of feeding in all treatment groups compared to the control, and remained elevated in the Group 4 following secession of supplementation. Superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and serum paraoxonase PON1 (U/L) showed similar trends. All of these parameters play a significant role in either oxygen supplementation of tissues, or anabolic and catabolic processes that on molecular levels contribute to the overall health and immune-building capacity of cells and tissues.3,6 The complete lack of mortality and increases in circulating cellular, biochemical and oxidative stress parameters suggest that the IMUNO-2865® represents a safe dietary supplement for aquaculture with an overall positive and potentially immunostimulative effect on the saltwater fish. A notable growth-promoting effect was present in juvenile freshwater chub. Further research warrants in vitro challenge studies to test the effectiveness of IMUNO-2865® supplementation in fish in controlled stress trials or infected with targeted pathogens.
Acknowledgements
The authors express their gratitude to Animal Necessity, LLC for funding this research, and to the fish farm Kornat Ittica for providing technical support. The results of this study were recently published in the Fish and Shellfish Immunology and Aquaculture Research.
* Presenting author
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