# Effects of Ocimum basilicum Essential Oil on Energy Metabolism, Oxidative Stress, Immune Response, and Metabolomics of Large Yellow Croaker (Larimichthys crocea) During Simulated Live Transport

## TL;DR

This study shows that Ocimum basilicum essential oil reduces stress and improves survival in large yellow croakers during transport.

## Contribution

The study reveals novel physiological and metabolic mechanisms by which OBEO reduces stress in transported fish.

## Key findings

- OBEO treatment reduced cortisol and HSP70 levels while increasing liver antioxidant enzyme activity.
- OBEO upregulated genes related to oxidative stress and inflammation, enhancing fish resilience.
- OBEO altered intestinal microbiota and key metabolic pathways to mitigate liver damage and boost immunity.

## Abstract

The biggest challenge in long-distance transport of fish is the high mortality rate caused by stress and oxidative damage. This study aimed to investigate and evaluate the effects of Ocimum basilicum essential oil (OBEO) on oxidative stress, immunity, inflammatory response, and intestinal microbiota and metabolism of yellow croaker during simulated transport. The large yellow croakers were placed in a 5 mg/L OBEO solution and a control solution (0 mg/L OBEO) for 72 h. The results of this study showed that the samples treated with OBEO exhibited higher antioxidant and anti-inflammatory capabilities.

Ocimum basilicum essential oil (OBEO) is an effective anesthetic and sedative for large yellow croaker (Larimichthys crocea) during live transport. This study aimed to assess the impact of OBEO on various physiological and biochemical parameters during live transport, thereby enhancing animal welfare and survival. Fish were exposed to 0 and 5 mg/L OBEO for 72 h during transport. Blood and liver samples were collected every 12 h after transport to evaluate blood biochemistry, tissue damage, oxidative stress-related and inflammation-related gene expression, intestinal microbiota, and liver metabolomics. The results demonstrated that the OBEO treatment significantly reduced serum cortisol levels and heat shock protein 70 (p < 0.05) while increasing the activity of liver antioxidant enzymes in large yellow croakers. Furthermore, compared to the control group, the expression of genes related to oxidative stress and inflammation was upregulated (p < 0.05), thereby enhancing the antioxidant and anti-inflammatory capacities of the fish. Microscopic examination of gill tissues revealed that OBEO alleviated morphological damage. Additionally, OBEO treatment altered the composition of intestinal microbiota, which contributed to the regulation of inflammatory responses. Moreover, liver metabolomics analysis identified key metabolic pathways, including arachidonic acid metabolism, steroid hormone biosynthesis, and amino acid metabolism, which could mitigate liver damage and enhance antioxidant and immune functions. In conclusion, OBEO effectively reduces transport stress in large yellow croakers through physiological, molecular, and metabolic mechanisms, providing a promising strategy to improve animal welfare and survival rate during live transport.