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Dietary tea tree essential oil addition to a low fishmeal diet containing high-Clostridium autoethanogenum protein diet improves the growth, lipid metabolism, antioxidant capacity and immunity of largemouth bass (Micropterus salmoides)

Year: 2025

Type: article

Abstract: The study aimed to explore the effects of adding tea tree essential oil (TTEO) to a low fishmeal diet on the growth, lipid metabolism, antioxidant capacity, and immunity of largemouth bass ( Micropterus salmoides ). Three isonitrogenous and isolipidic diets containing high- Clostridium autoethanogenum protein with dietary TTEO (0, 5 g/kg and 10 g/kg, and designated as Control, T5 and T10 groups) were formulated. A total of 360 largemouth basses (initial body weight: 15.06 ± 0.05 g) were randomly distributed into 9 cages and fed these diets for 8 weeks. Compared to the control group, supplementation of 5 g/kg of TTEO could significantly improve the weight gain rate (WGR) and specific growth rate (SGR) ( P < 0.05). The intestinal trypsin activity in the T5 group was significantly higher than in the control group ( P < 0.05). Compared to the control group, the addition of 5 g/kg of dietary TTEO elevated the total protein (TP) and albumin (ALB) contents, and decreased glucose (GLU) content and the total amount of transaminases ( P < 0.05). The triglyceride (TG) contents in serum and crude lipid in the liver of the T5 group were significantly reduced ( P < 0.05). Compared to the control group, TTEO could promote β-oxidation of fatty acid by upregulating the expression of peroxisome proliferator activated receptor alpha ( ppar-α ), carnitine palmitoyl-transferase 1 ( cpt-1 ), and downregulating acetyl-CoA carboxylase beta ( acc-β ) ( P < 0.05). In antioxidative parameters, 5 g/kg of dietary TTEO significantly reduced the contents of malondialdehyde (MDA) and protein carbonyls (PC) in serum, liver and intestine, and increased the total antioxidant capacity (T-AOC) in serum and superoxide dismutase (SOD) activity in serum and intestine compared with the control group ( P < 0.05). Histology analysis observed that 5 g/kg of dietary TTEO ameliorated vacuolization and nuclear excursion of hepatocytes induced by a low fish meal diet. After Aeromonas hydrophila administration, TTEO could upregulate the expression levels of anti-inflammatory-related genes such as il-10 and tgf-β1 compared with the control group ( P < 0.05). In conclusion, 5 g/kg TTEO supplementation in a low fish meal diet could promote growth performance, reduce lipid deposition, enhance liver health, and improve antioxidant capacity and immunity of largemouth bass. • Dietary tea tree essential oil (TTEO) in a low fish meal diet could improve the growth performance of largemouth bass. • Dietary TTEO could improve the antioxidative capacity and immunity through the Keap1-Nrf2 and TLR2-MyD88 pathways. • TTEO also promoted hepatic β-oxidation of fatty acids to reduce lipid deposition.

Source: Aquaculture Reports

DOI: 10.1016/j.aqrep.2025.102891