Starvation and re-feeding influence the growth, immune response, and intestinal microbiota of Nile tilapia (Oreochromis niloticus; Linnaeus 1758)

In the present study, the impacts of starvation and re-feeding on growth, immune response, and intestinal microbiota in Nile tilapia were evaluated. During starvation, the growth performance parameters including body weight (BW), feed conversion ratio (FCR), viscerosomatic index (VSI), and condition factor (CF) significantly decreased while increased after re-fed (p < 0.05). The activities of the digestive enzymes including lipase, amylase, and protease in the intestinal mucus significantly decreased in the starved group while increased after re-fed. After 14 days of starvation, the activities of non-specific immunological parameters including lysozyme (LZM), alkaline phosphate (ALP), and acid phosphate (ACP), and antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) in the liver were significantly increased. Also, the mRNA levels of inflammatory-related genes (interleukin -1beta IL-1 beta, interleukin -6 IL-6, and tumor necrosis factor TNF-alpha) in spleen were significantly up-regulated. The liver suppressor of cytokine signaling-1 (SOCS-1) mRNA expression level was significantly increased after 7 days and then decreased after 21 days of starvation which is seen to be responsible for the down-regulation of growth hormone (GH) signaling in the liver. In the liver, the mRNA expression levels of suppressor of cytokine signaling -2 (SOCS-2) increased while mRNA expression levels of suppressor of cytokine signaling-1 (SOCS-1) were significantly increased after 7 days and decreased after 21 days of starvation. Moreover, starvation influences the abundance and diversity of the intestinal microbiota of Nile tilapia. Also, the functional pathways of the intestinal microbiota were induced by starvation including energy metabolism, amino acid metabolism, carbohydrate metabolism, nucleotide metabolism, and lipid metabolism. These data will provide a better understanding of growth, immunity, and adaptability to environmental changes to Nile tilapia.