THE USE OF DIETARY HYDROLYSABLE TANNINS AS A PROPHYLACTIC STRATEGY IN AQUACULTURE

Tannins are water-soluble polyphenols commonly found in higher herbaceous and woody plants. Those extracted from sweet chestnut Castanea sativa, classified as hydrolysable tannins (HT), consist of esters of ellagic acid with core molecules composed of polyols such as carbohydrates and phenolics. As reported, HT possess a wide range of properties, such as antimicrobial, antioxidant, immunostimulant, anti-inflammatory, etc., that could result in an improvement of the intestinal health, growth, and disease resistance. Indeed, the benefits of HT as functional feed additives in terrestrial farm animals have been reported in different studies. However, there is limited literature on the effect of tannins on fish production, and practically no data available regarding their effect on cultured shrimp. For this reason, the present studies were aimed at assessing the effects of dietary HT from sweet chestnut on different parameters in shrimp and different species of fish.

Three 60-day feeding trials were carried out in parallel in Guangdong Ocean University, China, in three different species: catfish (Ictalurus punctatus), shrimp (Litopenaeus vannamei), and brown-marbled grouper (Epinephelus fuscoguttatus). In addition, a 28-week feeding trial was carried out in a commercial red tilapia (Oreochromis sp.) farm in Thailand. The experimental diets were a control diet (C) and three basal diets including different amounts of Farmatan Aqua, a tannin-rich extract bound to protein (0.1% FA, 0.2% FA and 0.3% FA). Parameters of growth performance, immune and antioxidant systems, and gut microbial populations were evaluated.

After 60 days of experimental feeding, a significant improvement (p < 0.05) was observed in the growth performance and survival of the animals fed diets including Farmatan Aqua in the four species. The activities of superoxide dismutase (SOD) and nitric oxide synthase (iNOS) were also higher in grouper and catfish fed the experimental diets than in those fed C during the majority of the experimental period. Results pointed out the positive effects of a dietary inclusion of 0.1 - 0.3% of Farmatan Aqua of as functional feed additive in shrimp and fish diets. Full results on all the assessed parameters in the four species will be further presented and discussed.