Effect of dietary Lactobacillus fermentum and lactulose on fatty acid profile and heavy metal residues in rainbow trout (Oncorhynchus mykiss)

Recently, demands upon the consumption of various seafood are increasing in a human diet. Heavy metals naturally occur in the environment and contamination of foodstuffs are causing great concerns. This study was aimed to investigate the effects of encapsulated and lyophilized Lactobacillus fermentum as probiotic and lactulose on heavy metal residues and fatty acid profile in rainbow trout. Thus, fishes were randomly allocated into three replicates of six different treatments. The experimental groups received basal diet (control group), basal diet plus lactulose, basal diet plus lyophilized L. fermentum and lactulose, basal diet plus encapsulated L. fermentum and lactulose, basal diet plus lyophilized L. fermentum, basal diet plus encapsulated L. fermentum. All the groups were fed three times daily for a period of 56 days. At the end of experiments, samples of the fillet and liver were taken. Our results showed that encapsulated L. fermentum and lactulose as synbiotic, significantly increased n-6 fatty acid in muscles and reduced moisture (p< 0.05). This supplementary diet significantly reduced Pb and Cd residues in muscles and Pb, Zn and Cd residues in liver (p< 0.05). Results showed that using encapsulated L. fermentum and lactulose in the diet improve the overall quality of fish.