Effect of Oral Administration of Red Alga (Laurencia caspica) Hydroalcoholic Extract on Growth Performance, Hematological Indices and Serum Biochemistry in Rainbow Trout (Oncorhynchus mykiss)

The use of natural immune stimulants is one of the most effective methods for strengthening immunity and preventing diseases in fish.

Due to the abundance of red algae (Laurencia caspica) in the Caspian Sea, the aim of this study was to investigate the effect of this algae on growth performance and blood indices of rainbow trout.

The present study was performed on 750 randomly selected rainbow trout (Oncorhynchus mykiss) in 5 experimental treatments including an algal extract-free diet (control), and diets supplemented with 0.5, 1, 1.5, and 2% of algal hydroalcoholic extract. During the experimental period, fish were sampled to measure growth performance and blood indices every two week for 8 weeks.

Growth indices were not affected by the algal extract at the end of eight weeks of feeding. There were no significant differences in fish survival at different treatments. Total counts of red blood cells, white blood cells, hematocrit percentage, hemoglobin concentration and neutrophil and monocyte percentages were affected by algal extract with significant increases compared to the control group (p < /em><0.05). Results of serum biochemistry showed that significantly increased total protein, albumin and globulin and also significantly reduced ALT, AST and ALP compared to the control in rainbow trout.

Based on the results of this study oral use of red algae (L. caspica) as an immune stimulant in rainbow trout (O. mykiss) was recommended.