Evaluation of immunostimulating and antibacterial properties of the AQUATAN feed additive in the rainbow trout (Parasalmo mykiss irideus)

Abstract

The article presents the results of research work on testing the effect of AQUATAN, a feed additive based on hydrolysable ellagitannins (extract of sweet chestnut wood, Castanea sativa Mill), on the rainbow trout. Experimental tests conducted for 93 days showed that AQUATAN at a dose of 2 g/kg introduced into the diet of the trout had an immunostimulating and antibacterial effect. There was a positive trend towards an increase in measurements of red blood cells (haemoglobin levels, RBC count) in the rainbow trout. An increase in the percentage of neutrophils, active phagocytic cells involved in the cellular component of immune system and performing phagocytosis and lysis of foreign agents, was revealed. The fish receiving the feed additive showed lower contamination of organs and blood with bacterial microflora. In the microbiocenosis, the number of isolated bacteria was two times lower compared to the fish that did not receive AQUATAN. Notably, there were no highly pathogenic Aeromonas strains, which are potential causative agents of aeromonosis or bacterial haemorrhagic septicaemia in fish, as well as Pseudomonadaceae (causative agents of pseudomonosis), Staphylococcus, Moraxella or coliform bacteria. Given the slow manifestation of the immunostimulating effect, regular use of the AQUATAN feed additive in the diet of the rainbow trout is advisable.