# Effects of Dietary Peanut Skin Proanthocyanidin Supplementation on Antioxidant Capacity and Intestinal Health of Juvenile American Eels (Anguilla rostrata)

## TL;DR

Adding peanut skin proanthocyanidins to the diet of juvenile American eels improves their antioxidant levels and gut health, with the best results at 900 mg/kg.

## Contribution

This study identifies peanut skin proanthocyanidins as a cost-effective alternative to grape seed proanthocyanidins for improving eel health.

## Key findings

- PSPc supplementation increased antioxidant enzyme activities and reduced oxidative stress markers in eels.
- Optimal intestinal health improvements were observed at 900 mg/kg PSPc, including enhanced villus height and enzyme activity.
- PSPc at 900 mg/kg altered gut microbiota composition, increasing beneficial bacteria and reducing harmful ones.

## Abstract

Proanthocyanidins from grape seeds are widely used as functional aquafeed additives for aquatic animals, but their high cost and limited domestic supply restrict widespread application. Peanut skins, a common agricultural byproduct, are rich in proanthocyanidins, offering a low-cost alternative resource. This study concentrates on evaluating the effects of peanut skin proanthocyanidins on the antioxidant capacity and intestinal health of juvenile American eels, and deeply analyzes the underlying mechanisms by which peanut skin proanthocyanidins enhance the antioxidant capacity and improve intestinal health of the experimental animals.

This study was performed to explore the influences of dietary peanut skin proanthocyanidins (PSPcs) on the antioxidant capability and intestinal health of juvenile American eels (Anguilla rostrata). The American eels (10.50 ± 0.03 g) were randomly allocated to five groups. Five experimental diets were formulated with graded levels of PSPc supplementation, and designated as PSPc0, PSPc300, PSPc600, PSPc900, and PSPc1200, respectively. The feeding experiment lasted for 8 weeks. In comparison with the PSPc0 group, the PSPc supplementation groups exhibited higher total antioxidant capacity and elevated levels of reduced glutathione, along with increased activities of superoxide dismutase, catalase, glutathione peroxidase, and glutathione S-transferase in the serum, liver, and intestine (p < 0.05). Dietary PSPc supplementation significantly decreased malondialdehyde levels in the serum, liver, and intestine (p < 0.05) and down-regulated hydrogen peroxide and nitric oxide levels in the liver and intestine (p < 0.05). Dietary PSPc supplementation also enhanced hepatic and intestinal anti-free radical superoxide anion and anti-free radical hydroxyl capacities (p < 0.05). Most of these parameters peaked in the PSPc900 group. PSPc supplementation in the diet increased villus height and muscular thickness and elevated activities of intestinal lipase and protease (p < 0.05), with lipase activity being the highest in the PSPc900 group. Compared with the PSPc900 group, the above-mentioned parameters in the PSPc1200 group showed a negative effect. Relative to the PSPc0 group, the PSPc900 group exhibited an increased relative abundance of Xanthomonadaceae and reduced relative abundances of Citrobacter, Chroococcidiopsis, Escherichia Shigella, Cupriavidus, Pelomonas, and Romboutsia (p < 0.05). Taken together, appropriate dietary PSPc supplementation improves antioxidant capacity and intestinal health in American eels, and the optimal dietary supplementation level is recommended at 900 mg/kg.