Effect of Dietary Lactobacillus plantarum Supplementation on the Growth Performance, Intestinal Health, Antioxidant Capacity, and mTOR Signaling Pathway of Juvenile Coho Salmon (Oncorhynchus kisutch)

This study investigates the effect of dietary <i>Lactobacillus plantarum</i> supplementation on juvenile coho salmon (<i>Oncorhynchus kisutch</i>). Four groups of the juveniles (initial weight 103.87 ± 2.65 g) were fed for 10 weeks with four diets containing 0 (control diet), 10⁵ (T1), 10⁷ (T2), and 10⁹ (T3) cfu/g of <i>L. plantarum</i>. The main results are as follows: Compared with the control diet, the final weight, specific growth rate (SGR), and weight gain rate (WGR) of the juveniles fed the T1, T2, and T3 diet significantly (<i>p</i> < 0.05) increased, while the feed coefficient ratio (FCR) expressed an opposite trend. The activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-PX) in the serum of the juveniles fed the T2 diet significantly (<i>p</i> < 0.05) increased, while the malondialdehyde (MDA) expressed an opposite trend. The expression of phosphatidylinositol 4,5-bisphosphate 3-kinase (<i>pi3k</i>), AKT-interacting protein (<i>akt</i>), mechanistic target of rapamycin kinase (<i>mtor</i>), glucose-6-phosphate dehydrogenase (<i>g6pd</i>), <i>sod</i>, <i>cat</i>, and <i>gsh-px</i> genes in the liver of the juveniles fed the T2 diet significantly (<i>p</i> < 0.05) increased. In conclusion, the T2 diet significantly improved the growth performance, antioxidant capacity, and upregulated key mTOR pathway genes in juvenile coho salmon.