Exploring the interactive effects of Thymol oil thymus serpyllum and Pediococcus acidilactici: Moving towards an enhanced performance, hematology, immunity and gut histology of Nile Tilapia (Oreochromis niloticus)

An 84-day experimental trial was conducted to investigate the effects of dietary thymol, P. acidilacticiat separate or combined on growth performance, intestinal digestive enzymes, bacterial counts, intestinal histo-morphometric indices, hemato-biochemical indices, and antioxidant responses in Nile tilapia, Oreochromis niloticus. A basal diet (30.34 g kg⁻¹ of crude protein) and isocaloric (19.21 MJ kg⁻¹ gross energy) was used to form the the experimental treatments. Control group was the basal diet without additives and the other three formulated diets were supplemented with 2.32 thymol mg kg⁻¹ diet or P. acidilacticiat 2 × 10⁹ CFU kg⁻¹ (probiotic; pro), and their mixture. 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 and feed conversion ratio (FCR) were recorded in fish fed diet containing a mixture of Thymol + P. acidilacticia. The activity of endogenous enzymes including; amylase, lipase, trypsin, and chymotrypsin was substantially boosted (P≤0.05) by supplemental diets with Thymol + P. acidilacticiat. Furthermore, fish fed diet supplemented with Thymol + P. acidilacticiat had greater villi width, villi height, goblet cells, absorption area, muscularis mucosa, and muscularis. Diets supplemented with a mixture of Thymol + P. acidilacticiat substantially improved hematological markers. The supplemental diets with Thymol + P. acidilacticiat improved the activities of catalase (CAT), glutathione peroxidase (Gpx), superoxide dismutase (SOD), and total antioxidant capacity (TAC) versus basal diet. In conclusion, the synergetic effect between Thymol + P. acidilacticiat ameliorated the growth, feed efficiency, intestinal digestive enzymes, intestinal histological morphometric, hemato-biochemical indices, and antioxidant responses of Nile tilapia.