Long-term effects of probiotics on health biochemical indices of serum and mucus in Rainbow trout (Oncorhynchus mykiss)

The object of this study was to evaluate the long-term effects of Lactobacillus fermentum, Lactobacillus buchneri and Saccharomyces cerevisiae, on serum and mucus biochemical indices as health indicator of rainbow trout (Oncorhynchus mykiss) at growing phase. A total of 160 fish with average weight of 250±50 g was divided into 8 groups and fed by diet supplemented with 10⁷ CFU g^-1 of each probiotic for 60 days in singular or combined feeding trail. The results showed that long-term feeding of probiotic supplemented diet increased serum alanine aminotransferase while reduced both serum and mucus alkaline phosphatase level. The probiotic supplements had no significant effects serum aspartateaminotransferase and mucus total protein by days 30 or 60 of experiment. In conclusion the results of this experiment showed that long-term feeding on probiotic supplemented diets may have adverse effects on health of rainbow trout and accordingly, it is not recommended to feed fish for more than 30 days on probiotic supplemented diets.