Effects of dietary phytol supplementation on growth performance, immunological parameters, intestinal bacteria, and prevention of oxidative stress following transportation of Nile tilapia, Oreochromis niloticus

Abstract

In this study, Nile tilapia, Oreochromis niloticus, fingerlings (2.00 ± 0.02) were fed diets (crude protein 345 g/kg; crude lipid 86.8 g/kg) containing 0 (CTL), 75 (PH-75), 150 (PH-150), and 300 (PH-300) mg/kg phytol for 60 days, at 4% of biomass. The fish were reared in sixteen 70-L tanks (n = 4, each with 40 fish). After 60 days rearing, the fish were subjected to 6-h transportation to monitor the hepatic antioxidant parameters. The results showed that dietary 75 mg/kg phytol significantly improved fish growth (P < 0.001) and feed efficiency (P = 0.015). Plasma lysozyme (P = 0.004) alternative complement (P = 0.006), alkaline phosphatase (P = 0.014) significantly increased in PH-75, 75PH/150PH, and PH-75/PH-300 treatments, respectively. All phytol-treatments led to significant (P = 0.001) increase in the blood neutrophil count. The PH-300 treatment resulted in significantly higher blood WBC (P = 0.008), monocyte (P = 0.010), and eosinophil (P < 0.001) counts, compared to CTL. Phytol also modulated intestinal microbiota by reducing the number of total viable bacteria in PH-75 and PH-150 (P = 0.027) and increasing lactic acid bacteria in PH-75 (P = 0.017). PH-75 and PH-150 had highest survival, antioxidant enzymes, reduced glutathione levels, lowest lipid peroxidation, before and/or after the transportation. PH-300 treatment showed an elevation lipid peroxidation, after the transportation. These findings suggest that dietary phytol may be a good supplement for improving the health and growth performance of Nile tilapia, and the recommended level is 75 mg/kg.