Effects of Dietary Phytol Supplementation on Growth Performance, Immunological Parameters, Intestinal Bacteria, and Prevention of Oxidative Stress Following Transportation of Nile Tilapia, <i>Oreochromis niloticus</i>
Saman Ahani, Sara Ahani, Morteza Yousefi, Ali Taheri Mirghaed, Afaf N. Abdel Rahman
Abstract
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 < 0.001). 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‐150; the highest activities were related to PH‐75 and PH‐150 treatments, which had also the highest post‐transportation survivals ( P < 0.001). In conclusion, phytol is a suitable feed supplement for Nile tilapia, improving growth performance and welfare, particularly at 75 mg/kg.