Effects of dietary Phytol Supplementation on Growth Performance, Immunological Parameters, Intestinal Bacteria, and Prevention of Oxidative Stress Following Transportation of Nile Tilapia, Oreochromis niloticus

Nile tilapia, Oreochromis niloticus. (2.00 0.02 g) were reared in 16 70-L. tanks (40 individual/tank) and fed diets (approx. 345 g/kg protein, approx. 87 g/kg crude fat) containing 0 (CTL), 75 (PH-75), 150 (PH-150), and 300 (PH-300) mg/kg phytol (n = 4).After 60 days of feeding (4% daily), growth performance, humoral immune parameters, and gut bacteria were analyzed. Also, hepatic antioxidant parameters were determined before and after the fish were transported in plastic bags for 6 hr. The results showed that PH-75 exhibited the highest final weight (P < 0,001), weight gain (P < 0.001), feed intake (P < 0.001), feed efficiency (P - 0.015), plasma lysozyme activity (P = 0.004),and intestinal Lactobacillus sp. population (P = 0.017), among the treatments. The highest plasma alternative complement activity (P = 0.006) and the lowest intestinal total viable bacteria (P = 0.027) were observed in PH-75 and PH-150. The highest plasma alkaline phosphatase activities were observed in PH-75 and PH-300 (P = 0.014). The highest blood leukocyte (P = 0.008). monocyte (P = 0.010), and eosinophil (P < 0.001) were observed in PH-300, while the highest blood neutrophil was observed in all phytol treatments (P < 0,00l). The highest hepatic lipid peroxidation was observed in PH-300, whereas PH-75 and PH- 150 showed the lowest values (P < 0.001). The highest hepatic reduced glutathione was observed in PH-75, also PH-150 exhibited significant elevation in this parameter, compared to CTL (P < 0.001). Transportation led to significant elevations in the hepatic antioxidant enzymes' activities in CTL, PH-75, and PH- I50; the highest activities were related to PH-75 and PH- I50 treatments, which had also the highest post-transportation survivals (P < 0.00l). In conclusion, phytol is a suitable feed supplement for Nile tilapia, improving growth performance and welfare, particularly at 75 mg/kg.