Effect of Lyophilized, Encapsulated Lactobacillus fermentum and Lactulose Feeding on Growth Performance, Heavy Metals, and Trace Element Residues in Rainbow Trout (Oncorhynchus mykiss) Tissues.

Heavy metals naturally occur in the environment and are causing great concern all around the world. Accumulation of heavy metals in fish tissues can lead to serious adverse effects in humans when consumed in the amounts exceeding the safe consumption levels. In this study, Lactobacillus fermentum 1744 (ATCC 14931) and lactulose were used in the fish diet in order to investigate their effects on growth performance, intestinal villous morphology, and heavy metals residues. Fishes were randomly allocated into three replicates of five different treatments. The control group received the basal diet, while the experimental groups were fed on the basal diet supplemented with encapsulated and lyophillized probiotic, lactulose (prebiotic) and L. fermentum, and lactulose as synbiotic. All the groups were fed three times daily for a period of 56 days. At the end of growth period, 10 fish per replicate were randomly collected in order to take the samples of the fillet, gills, and liver. Results showed that the encapsulated L. fermentum plus lactulose improve growth performance and exclude absorption and accumulation of heavy metals in rainbow trout liver and gills. The villous height were increased in all the samples except the group 2 fed on the lactulose (p < 0.05).