# Impact of organic and nano selenium on sexual maturation, egg, and offspring quality of European sea bass (Dicentrarchus labrax) broodstock

## TL;DR

This study shows that adding selenium to sea bass diets improves their reproduction and offspring quality.

## Contribution

The novel finding is that both nano and organic selenium supplementation significantly enhances reproductive hormones and offspring viability in European sea bass.

## Key findings

- Selenium supplementation increased reproductive hormones like LH, FSH, testosterone, and estradiol in sea bass.
- Nano and organic selenium improved egg quality, hatchability, and larval survival compared to the control group.
- Supplemented diets enhanced plasma protein levels and antioxidant activity in broodstock.

## Abstract

The current research investigated the impact of different types of Selenium fortification in European sea bass (Dicentrarchus labrax) broodstock diets on sexual maturation, spawning, egg quality, and offspring quality. The study lasted 85 days and involved 54 broodstock during their maturation period. The broodstock received daily nourishment amounting to 5% of their body weight based on three distinct dietary regimens: a control diet, the basal diet without Selenium supplementation (C), a basal diet supplemented with 0.3 mg of nanoparticle Selenium per kg (N-Se), and a basal diet supplemented with 4 mg of organic Selenium per kg (O-Se). Each dietary regimen was replicated three times. The diets for broodstock were carefully formulated and consisted of squid, dry feed containing 45% protein, and sardines. The broodstock was housed in nine circular fiberglass tanks, each with a capacity of 20 m3, accommodating three males and three females per tank. However, each tank had a practical volume of 16 m3. The males’ average weight is 1.15 ± 0.05 kg, and measured 41 ± 2 cm in length, while the females’ average weight is 2.0 ± 0.2 kg and measured 52 ± 2 cm. After the feeding treatment, the broodstock was injected with 13 µg/kg of LHRH analog to induce spawning. The water in the tanks was replaced daily with filtered seawater. The tanks were maintained on a 10:30 h light cycle followed by 13:30 h of darkness daily. The water quality was kept within a suitable range for marine fish conditions, including temperature, pH, salinity, and total ammonia nitrogen. The broodstock fed the experimental diets showed significant increases in reproductive performance hormones, including luteinizing hormone (LH), follicle-stimulating hormone (FSH), testosterone (T), and estradiol (E), in both male and female sea bass. Fish-fed diets containing N-Se and O-Se resulted in significantly higher hormone levels (P ≤ 0.001) compared to the control diet. Additionally, they exhibited elevated levels of total protein, albumin, globulin, and specific lysozyme activity in their plasma, which was significantly greater than that observed in the control group (P < 0.05). In contrast, the control group (Group C) exhibited increased levels of total lipids, cholesterol, and triglycerides. Incorporating Selenium into diets significantly enhanced reproductive performance, egg quality, egg diameter, hatchability, and the size of newly hatched larvae. Fertility rates, egg diameter, oil droplet diameter, and the percentage of fertilized and viable eggs all showed significant improvement when diets were supplemented with nano and organic Selenium compared to the control group. Furthermore, the survival rate and glutathione peroxidase (GPx) levels in larvae from broodstock fed diets enriched with nano and organic Selenium were superior to those observed in the control diet, as indicated in 15 DPH.