Effects of prebiotic Immunogen on growth performance, intestinal bacteria colonization, and survival rate in Rutilus frisii fry

This study was carried out to determine the effects of Immunogen as a prebiotic on growth related parameters and gut micro-flora in R. frisii fry. A basal diet was formulated using common feed ingredients supplemented with Immunogen at 0, 1, 1.5, and 2 g.kg-1 leading to four experimental diets. Fish were randomly distributed in 500 L fiberglass tanks (1×1×0.5 m). The experiment lasted for eight weeks and the water temperature ranged between 21-24 °C. R. frisii fry with an initial weight of 300 ± 1.7 mg and were randomly distributed in the experimental tanks. At the end of the experiment, growth performance, feed efficiency, and gut micro-flora were assessed. Results showed that inclusion of 1g.kg-1 Immunogen improved final weight, feed conversion efficiency (FCR), and specific growth rate (SGR) (p<0.01) in the fry. A larger survival rate of R. frisii fry was observed at 1 g kg-1 prebiotic inclusion level (p<0.01). However, body protein, fat, and ash were not influenced by prebiotic inclusion. Supplementation of 1 g.kg-1 prebiotic increased the total count of bacteria (p<0.05), but bacterial count did not change at 1.5 and 2 g.kg-1 prebiotic inclusion compared to control diet. In conclusion, Immunogen administration of 1 g. kg- 1 is capable of improving the nutrients efficiency and performance of R. frisii fry through growth stimulation of beneficial intestinal bacteria.