The potential synergistic action of quercetin and/or Pediococcus acidilactici on Nile tilapia, Oreochromis niloticus performance

An 84-day experimental trial was conducted to investigate the effects of dietary quercetin, Pediococcus acidilactici or combined on growth performance, intestinal digestive enzymes, feed utilization, bacterial counts, intestinal histo-morphometric indices, hemato-biochemical indices, and antioxidant responses in Nile tilapia, Oreochromis niloticus. Four isonitrogenous (30.34 g kg(-1) of crude protein) and isocaloric (19.21 MJ kg(-1) gross energy) diets were formulated from practical ingredients. The first diet was the control diet. The other three formulated diets were supplemented with 5 g quercetin (quer) kg(-1) diet or P. acidilacticiat 2 x 10(9) CFU kg(- 1) (probiotic; pro), and their mixture 5 g quercetin kg(-1) + 2 x 10(9) P. acidilactici (CFU kg(- 1)) (pro-quer). A total number of 300 healthy fingerlings (Initial average weight 4.51 +/- 0.01 g) were randomly allocated into four groups (25 fish for each group in triplicates). The results showed that the best values of growth, feed efficiency, and feed conversion ratio (FCR) were recorded in fish fed diet containing pro-quer. The activity of endogenous enzymes including; amylase, lipase, trypsin, and chymotrypsin was substantially boosted (P < 0.05) by supplemental diets with quercetin, probiotic, and pro-quer. Furthermore, fish fed diet supplemented with pro-quer had greater villi width, villi height, goblet cells, absorption area, muscularis mucosa, and muscularis. The highest total intestinal and gut bacterial counts were detected in fish fed diet supplemental with probiotic. Diets supplemented with quercetin, probiotic, and pro-quer substantially improved hematological markers including hematocrit (Htc), hemoglobin (Hb), red blood cell (RBC), and white blood cell (WBC) counts. The fish given a pro-quer diet had the lowest significant (P < 0.05) ALT value, whereas that fed quercetin had the lowest AST value. Serum total protein, globulin, and albumin levels were higher (P < 0.05) in fish fed diets containing quercetin, probiotic, and pro-quer compared to the control diet, with the greatest levels found in those fed diet supplemented with quercetin. However, supplementation of quercetin, probiotic, and pro-quer, lowered the levels of cholesterol, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and triglyceride. The supplemental diets with quercetin, probiotic, and pro-quer improved the activities of catalase (CAT), glutathione peroxidase (Gpx), superoxide dismutase (SOD), and total antioxidant capacity (TAC) compared with the control diet. In conclusion, the synergetic effect between quercetin and probiotic ameliorated the growth, feed efficiency, intestinal digestive enzymes, intestinal histological morphometric, hemato-biochemical indices, and antioxidant responses of Nile tilapia.