Camphor oil-enriched diets: Impact on growth, immune response, and gonadal development of Nile tilapia

This study investigates the impact of camphor oil in Nile tilapia (Oreochromis niloticus) diets on growth performance, immune responses, lipid metabolism, sex hormones, and gonads maturation. 450 mixed-sex fish of uniform size at a density of 30 fish/pond (15 cement ponds) were fed the experimental diets for 70 days. Five experimental diets were formulated, each diet supplemented with different levels of camphor oil: 0 (control), 2, 4, 6 and 8 g/kg diet. The results show that camphor oil (CO) significantly improved growth and feed utilization including weight gain (27.97 and 28.95 g), final body weight (39.68 and 40.63 g), specific growth rate (1.94 and 1.98 %), and protein efficiency ratio (1.98 and 1.99 g) at inclusion 2–4 g kg⁻¹ diets with insignificant differences between them (P > 0.05). The highest immune parameters such as immunoglobulin M (IgM), total protein, and albumin levels (P < 0.05) were detected in diet have camphor oil at 5 g kg^-1 (0.27 mg/dL, 2.78 g/dL, and 1.80 g/dL, respectively). Histological analyses revealed enhanced intestinal integrity and hepatic health at these optimal levels. However, higher inclusion levels (8 and 10 g kg⁻¹ diet) caused significant adverse effects, including histopathological damage in the liver and gonads, reduced nutrient absorption efficiency, and a marked decline in sex hormone concentrations (estradiol, progesterone, and testosterone) (P < 0.05). These detrimental effects are likely due to disrupted lipid metabolism, as reflected by significant reductions in cholesterol and triglycerides, which are essential substrates for steroidogenesis (P < 0.05). The findings underscore the potential of camphor oil as an eco-friendly alternative to synthetic additives, offering significant health benefits and improved performance at optimized levels. Nevertheless, precise dose optimization is critical to prevent toxicity and adverse effects.