Comparative Effects of Selenium Yeast and Sodium Selenite on the Selenium Distribution, Interior Quality and Oxidative Stability of Docosahexaenoic Acid-Enriched Eggs During Storage

Docosahexaenoic acid (DHA)-enriched eggs are nutritionally valuable for human cardiovascular health and neurodevelopment but face severe lipid oxidation during storage due to DHA's high degree of unsaturation, which reduces their quality and shelf life. Selenium (Se) mitigates such oxidation, yet the efficacy of different Se sources (organic vs. inorganic) in DHA-enriched eggs remains inadequately quantified. This study investigated the effects of dietary Se sources on Se distribution, internal quality, and oxidative stability of DHA-enriched eggs by feeding 360 Hy-line Brown laying hens (50 weeks old) four diets for 8 weeks: a basal diet (CON; analyzed Se: 0.10 mg/kg), a DHA-enriched microalgae diet (MA; analyzed Se: 0.11 mg/kg), or MA supplemented with 0.25 mg/kg Se as sodium selenite (MA + SS) or selenium yeast (MA + SY). At the end of the feeding trial, eggs were collected and stored at 22 °C for 0, 15, or 30 days to evaluate internal quality and oxidative stability. Results showed that SY was significantly more effective than SS in enriching Se in eggs: the total Se content in whole eggs of MA + SY (18.82 mg) was 39.6% higher than that of MA + SS (13.48 mg), with albumen Se content in MA + SY (0.239 mg/kg) being 2.17-fold that of MA + SS (0.110 mg/kg). Supplementation with DHA alone (MA diet) negatively impacted stored egg quality: at 30 days of storage, the Haugh unit (HU) of MA (54.93) was 10.6% lower than that of CON (61.48), and yolk thiobarbituric acid-reactive substances (TBARSs, 495.8 μg MDA/kg) was 22.9% higher than that of CON (403.3 μg MDA/kg). However, both Se sources improved these parameters, with SY showing a more pronounced effect: at 30 days, MA + SY had a higher yolk GPX activity (58.10 U/g protein, 12.1% higher than MA + SS) and lower yolk TBARSs (361.2 μg MDA/kg, 11.6% lower than MA + SS), while its HU (62.97) was restored to 99.2% of CON's level. The superior efficacy of SY was attributed to greater Se deposition and enhanced GPX activity, which jointly reduced lipid and protein oxidation. These findings confirm SY as the preferred Se supplement for producing nutritionally enhanced DHA-enriched eggs with improved storage stability.