“Evaluation of dietary black garlic peel as an alternative to antibiotics in rainbow trout (Oncorhynchus mykiss) (6982)”

Evaluation of dietary black garlic peel as an alternative to antibiotics in rainbow trout (Oncorhynchus mykiss)

Saeyeon Lim and Youngjin Park

Department of Aquatic Life Medical Sciences, Sunmoon University, Asan 31460, Republic of Korea

Introduction: Antibiotics are commonly used in aquaculture, but their misuse has raised concerns about resistance and environmental impact. Plant-derived bioactive compounds offer a safer, eco-friendly alternative with antioxidant and immune-enhancing benefits for fish. Black garlic peel is a by-product rich in polyphenols and flavonoids, exhibiting strong antioxidant activity. However, it is largely discarded and has been rarely studied as an aquafeed ingredient. This study aimed to evaluate the potential use of black garlic peel as a functional feed additive in rainbow trout, with a particular focus on its effects on liver health.

Methodology: Black garlic was prepared via thermal aging, and its peel was incorporated into a commercial trout diet at 0%, 1%, 2%, and 3%. Rainbow trout (13.6±0.7g, 11.5±0.2cm) were distributed into 120 L freshwater tanks (pH 7.4–7.6, DO 9–10 mg/L, 12.8±0.2°C) at 20 fish per group and fed for 8 weeks. Blood was collected for antioxidant analysis, and liver tissue was sampled for gene expression analysis.

Result: Growth performance significantly improved in the 3% group compared to the 0 % group. Blood biochemical analysis (SOD, GPx, GOT, GPT) showed increasing trends with higher inclusion levels, though not statistically significant.

RNA-sequencing revealed that metabolic and hepatic stress-related genes (pgm1, pla2g3, phka2, and mrpl9) were upregulated in the 3% group compared to those of 0% group. These results suggest increased hepatic metabolic activity and cellular stress. Notably, S-allyl cysteine (SAC), a major sulfur-containing compound abundant in black garlic peel, is known for its antioxidant and detoxifying effects at moderate levels. However, at higher concentrations, SAC may induce cytochrome P450 (CYP450) enzyme activity and elevate reactive oxygen species (ROS) production, potentially leading to oxidative stress and liver damage. The observed gene expression changes support the possibility of hepatotoxic effects under excessive dietary inclusion.

Conclusion: Black garlic peel may serve as a functional feed additive that promotes growth in rainbow trout when used at appropriate levels. However, its high-dose application may pose hepatotoxic risks, emphasizing the need for further studies to determine optimal dosage and long-term safety.

Keywords: black garlic peel, hepatotoxic, fish feed, rainbow trout

Funding: Sunmoon University, NRF (National Research Foundation of Korea)

1. Saeyeon, Lim, Sunmoon University, Presenter
2. Youngjin, Park, Sunmoon University, Author