Effects of Dietary Bee-Collected Chestnut Pollen on Growth Performance, Innate Immune Responses, and Antioxidant Defense in European Catfish (Silurus glanis) Reared at Different Stocking Densities

Dietary chestnut pollen may improve growth and immune responses in European catfish, but the practical implications require further investigation.

Summary and findings

This study evaluated the effects of dietary bee-collected chestnut pollen on growth performance and immune responses in European catfish. A total of 600 fish were assigned to different dietary treatments over 60 days. The study found significant improvements in various growth and immune parameters with dietary supplementation.

Abstract

<title>Abstract</title> <p> This study evaluated the effects of dietary bee-collected chestnut pollen ( <italic>Castanea sativa</italic> ) on growth performance, feed utilization, hematological characteristics, innate immune responses, and antioxidant defense in European catfish ( <italic>Silurus glanis</italic> ) reared under normal and high stocking density conditions. A total of 600 fish (initial body weight: 99.0 ± 1.0 g) were randomly assigned to a 2 × 4 factorial design with two initial stocking densities (6.6 and 9.9 kg m⁻³, corresponding to 20 and 30 fish per tank, respectively) and four dietary treatments: a control diet and diets (D1, D2, and D3) supplemented with 1%, 2%, or 4% chestnut pollen. Each treatment combination had three replicate tanks, and the feeding trial lasted 60 days. Chestnut pollen contained high levels of protein and unsaturated fatty acids and exhibited strong antioxidant capacity. Dietary supplementation significantly improved final body weight, weight gain, specific growth rate, feed efficiency ratio, and protein efficiency ratio while reducing feed conversion ratio under both stocking density conditions ( <italic>P</italic>  < 0.05). Dietary supplementation also enhanced innate immune responses, as evidenced by increased leukocyte count, nitroblue tetrazolium reduction activity, total protein, immunoglobulin M, myeloperoxidase activity, lysozyme activity, and bactericidal activity ( <italic>P</italic>  < 0.05). Furthermore, supplementation reduced malondialdehyde concentrations and increased superoxide dismutase, catalase, glutathione peroxidase, and reduced glutathione levels in both liver and kidney tissues ( <italic>P</italic>  < 0.05), reflecting improved antioxidant status and reduced oxidative stress. Stocking density, dietary treatment, and their interaction significantly affected most variables evaluated ( <italic>P</italic>  < 0.05). Although the 2% and 4% diets produced comparable biological responses, the 2% inclusion level provided similar benefits with greater economic efficiency. These findings support the use of dietary chestnut pollen as a functional feed ingredient to improve growth performance, innate immunity, and antioxidant defense in European catfish reared under intensive farming conditions. </p>

Elsewhere in the Glutathione (GSH) corpus