Introduction: Medicinal plants, containing natural active compounds, possess antioxidant, anti-inflammatory, and antibacterial properties and can affect growth and blood parameters. The goldfish (Carassius auratus) is a resilient freshwater species that, due to its rapid growth and ease of maintenance, is widely used in research studies. This fish is recognized as a suitable biological model for examining the nutritional, physiological, and natural compounds effects. Plant-derived products are increasingly used in aquaculture as natural feed additives because they can enhance fish growth, immunity, and overall health through bioactive compounds. Therefore, this study aimed to investigate the effects of dietary supplementation with bay leaf (Laurus nobilis) essential oil on the growth and blood parameters of goldfish.
Materials and Methods: Initially, the fish with a mean initial weight of 2.42 ± 1.2 g (mean ± SD) were fed for 8 weeks with five different levels of bay leaf essential oil, including 0 (LN0), 5 (LN5), 10 (LN10), 15 (LN15), 20 (LN20), and 25 (LN25) g per kilogram of feed. To initiate the study, the fish were acclimated for two weeks and then distributed into glass aquariums with a water volume of 150 liters. Six treatments were considered for this experiment. The aquariums were placed in an indoor system, with water temperature ranging from 24 to 25 °C. To prepare the bay leaf essential oil, 3000 g of fresh leaves were placed in an oven for 24 hours at 50 °C until completely dried. Subsequently, for proximate composition analysis, the dried fresh leaves were sent to Barij Essence Pharmaceutical Company. Changes in growth parameters including final weight (FW), weight gain (WG), specific growth rate (SGR), feed conversion ratio (FCR), and body weight increase (BWI) were evaluated, along with blood parameters such as white blood cells count (WBC), red blood cells count (RBC), hemoglobin (Hb), hematocrit (Hct), and differential white blood cells percentage.
Results and Discussion: The LN20 treatment showed the best growth performance, exhibiting the highest FW, WG, SGR, and BWI compared to the other treatments (p< 0.05). Additionally, LN20 treatment had the lowest FCR compared to other treatments (p< 0.05). Regarding blood parameters, the LN10 and LN15 treatments exhibited the highest white and RBC, along with the highest Hb and Hct levels (p< 0.05). In contrast, the LN25 treatment had the lowest WBS and RBC cells counts. The highest lymphocyte percentage was observed in the LN10 and LN15 treatments, while lowest was in LN0. The neutrophil percentage was significantly affected by different levels of bay leaf essential oil (p< 0.05), with LN0 and LN5 showing the highest neutrophil levels and LN10 the lowest. Moreover, there was a significant difference in monocyte percentage among treatments (p< 0.05), with the highest value observed in LN20 and the lowest in LN25.
Conclusion: The results of study indicated that adding bay leaf essential oil to the diet of goldfish at levels of 10 to 20 g per kilogram of feed can significantly improve growth performance and hematological parameters. Based on these findings, the use of this supplement is recommended as an effective nutritional agent in aquaculture. |
