Effects of dietary selenium nanoparticles and pennyroyal essential oil on growth performance, immune-biochemical and antioxidant parameters and disease resistance in Nile tilapia, Oreochromis niloticus

This study aimed to evaluate the effects of dietary selenium nanoparticles (SeNPs) and pennyroyal essential oil (PE) on growth performance, antioxidant capacity, immunological responses, biochemical parameters, and disease resistance in Nile tilapia, Oreochromis niloticus. Fish with an average weight of 5.97 ± 0.37 g were randomly allocated into 12 plastic tanks, corresponding to four dietary treatments with three replicates. The dietary treatments included: control (CT, no supplementation), SE (supplemented with 1 mg/kg SeNPs), PE (supplemented with 250 mg/kg PE), and SE + PE (supplemented with 1 mg/kg SeNPs and 250 mg/kg PE) for a duration of eight weeks. Following the feeding period, the fish were intraperitoneally infected with Aeromonas hydrophila. No significant differences in feed conversion ratio were observed among the treatments; however, dietary PE significantly enhanced fish growth performance. Intestinal amylase activity was significantly elevated in the PE and SE + PE treatments; whereas intestinal lipase, protease, and alkaline phosphatase activities was significantly elevated in the PE treatment, compared to the CT group. Intestinal superoxide dismutase activity was significantly higher in all supplemented diet groups, compared to the CT treatment. Furthermore, intestinal catalase activity significantly increased, while malondialdehyde levels significantly decreased with dietary supplementation of either SeNPs or PE. Dietary PE supplementation led to a significant increase in intestinal glutathione peroxidase activity. Both SeNPs and PE supplementation significantly reduced plasma aminotransferase activities and hepatic malondialdehyde levels, but increased plasma and hepatic lysozyme and alternative complement activities, immunoglobulin levels, hepatic antioxidant enzyme activities, total antioxidant capacity, and reduced glutathione content. The supplemented diet groups exhibited similar post-infection mortality rates, which were significantly lower than that of the CT group. Moreover, dietary supplementation with SeNPs and PE significantly mitigated the effects of infection on plasma cortisol and glucose levels, plasma and hepatic aminotransferase activities, lysozyme and alternative complement activities, hepatic total antioxidant capacity, and reduced glutathione content. Additionally, these supplements significantly enhanced the effects of infection on hepatic superoxide dismutase and glutathione peroxidase activities. Among all post-infection parameters assessed, the SE + PE treatment demonstrated the most favorable outcomes, followed by the PE treatment. In conclusion, dietary supplementation with SeNPs and PE represents a beneficial strategy for enhancing Nile tilapia production and disease management. These additives exert their positive effects by improving digestive enzyme activity, enhancing antioxidant capacity, and bolstering immune responses, while simultaneously reducing stress levels. © 2025 Elsevier Ltd