Mitigating Heat Stress in the Nile Tilapia (Oreochromis niloticus) Using Dietary Nano Zinc Oxide: Impacts on Growth, Biochemistry, and Growth-Related Genes

Et Al., Abozaid

doi:10.21608/ejabf.2025.445336

Mitigating Heat Stress in the Nile Tilapia (Oreochromis niloticus) Using Dietary Nano Zinc Oxide: Impacts on Growth, Biochemistry, and Growth-Related Genes

Author

Abozaid et al.

10.21608/ejabf.2025.445336

Abstract

This study investigated the combined effects of dietary nano zinc oxide (N-ZnO) supplementation and rearing temperature on growth performance, blood biochemistry, and the expression of growth-related genes in the Nile tilapia (Oreochromis niloticus). A total of 180 fish (initial weight: 154.7 ± 0.48 g) were randomly assigned to six groups: a control group reared at 28°C, a heat-stressed control at 34°C, and four treatment groups fed diets containing 15 or 30mg/ kg N-ZnO at either 28°C or 34°C. The feeding trial lasted 75 days, with heat stress applied during the final 15 days.
N-ZnO supplementation significantly improved final body weight, weight gain, feed intake, and feed conversion ratio, with the most pronounced effects observed at 30mg/ kg under normal temperature conditions. Although heat stress negatively impacted growth parameters, dietary N-ZnO mitigated these adverse effects. Biochemical analyses revealed that elevated temperature reduced serum AST and ALT levels in control fish, whereas N-ZnO supplementation helped restore these enzyme levels toward normal ranges. In contrast, urea, creatinine, and cholesterol levels were not significantly influenced by either temperature or dietary treatment. Gene expression analysis showed that supplementation with 15mg/ kg N-ZnO at 34°C upregulated IGF1 and GH expression in liver tissue, while 30mg/ kg at the same temperature increased IGF2 expression. In gill tissue, the highest expression levels of IGF1 and IGF2 were observed at 30mg/ kg under 28°C, whereas GH expression peaked at 15mg/ kg under 34°C. These findings demonstrate that dietary N-ZnO, particularly at 15– 30mg/ kg, enhances growth performance, supports liver function, and promotes the expression of growth-related genes under thermal stress. This suggests its potential as a nutritional strategy for improving tilapia resilience and productivity in warming aquaculture environments.

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