Dietary Cyanus Depressus (M. Bieb.) Soják Plant Extract Enhances Growth Performance, Modulates Intestinal Microbiota, and Alters Gene Expression Associated With Digestion, Antioxidant, Stress, and Immune Responses in Rainbow Trout (Oncorhynchus Mykiss)

Abstract

This study aimed to assess the effects of dietary Cyanus depressus (CD) extract on rainbow trout (Oncorhynchus mykiss) physiology and health. Fish with an average weight of 3.29 +/- 0.34 g were allocated to four feeding groups, receiving diets containing CD extract at doses of 0 (Control), 0.5 (CD05), 1 (CD1), and 2 (CD2) g kg-1 for a period of 60 days. Results revealed significant improvements in final body weight, weight gain, and specific growth rate in groups supplemented with 1 and 2 g/kg of CD extract. Lipase activity increased notably in fish fed with CD0.5, CD1, and CD2 diets. The CD1 group exhibited the highest trypsin activity, while the groups receiving 1 g/kg and 2 g/kg of CD extract displayed the highest amylase activity. Analysis of gene expression levels for superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) showed marked increases across all groups compared to the control, with the most significant enhancement observed in fish fed with 2 g/kg of CD extract. Significant variations were observed in the expression of immunity-related genes among the treatments, with the highest expression levels of tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta) found in groups fed a diet enriched with CD extract. The increased activity of immune-related genes was more prominent in fish fed 2 g/kg of CD extract than in the control group. Notably, in fish fed with CD extract, heat shock protein 70 (HSP70) gene expression increased in the CD2 group, decreased in the CD05 group, and remained statistically unchanged in the CD1 group compared to the control. Additionally, supplementation with CD extract altered the composition and abundance of the intestinal microbiota in rainbow trout. In conclusion, our study suggests that Cyanus depressus extract has significant potential for enhancing various physiological and health aspects of rainbow trout, particularly when supplemented at 2 g/kg.