Inclusion of Dietary Defatted Microalgae Dose-Dependently Enriches ω-3 Fatty Acids in Egg Yolk and Tissues of Laying Hens

Background: The potential for dietary microalgae to enrich eggs of laying hens with omega-3 (n-3) fatty acids, and the mechanisms involved, are unclear. Objectives: The aim of this study was to determine the effects and molecular regulation of a defatted Nannochloropsis oceanica microalgae (DNOM) biomass on the enrichment of the eggs and tissues of laying hens with omega-3 fatty acids. Methods: Fifty Shaver-White Leghorn hens (46 wk of age, body weight: 1.70 +/- 0.27 kg) were individually caged (n = 10) and fed a corn-soy-based diet supplemented with DNOM at 0% (control), 2.86%, 5.75%, 11.5%, and 23% for 6 wk. Fatty acid profiles, health status, and related gene expression in eggs, blood, and tissues were performed at weeks 0, 2, 4, and 6. Data were analyzed by a combination of 1-factor ANOVA and correlation between DNOM doses and measures. Results: The DNOM produced linear (P < 0.01) enrichments of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and total omega-3 fatty acids in the egg yolk (R-2 > 0.9) and of DHA in the liver, breast, and thigh (R-2 = 0.66-0.82). Concentrations of EPA + DHA in the egg yolk and these 3 tissues of hens fed 11.5% and 23% DNOM were 1.4-2.1, 0.6-1, 3.3-5.3, and 6-7 times greater (P < 0.001) than those in the controls, respectively. The DNOM caused dose-dependent elevations (P < 0.01) of malic enzyme and elongases 3, 4, and 5 mRNA levels (R-2 = 0.97, 0.78, 0.97, and 0.86, respectively), along with increased (P < 0.01) Delta 5- and Delta 6-desaturases and decreased (P < 0.01) Delta 9-desaturase and acyl-coenzyme A thioesterase 4 mRNA levels in the liver. Conclusions: Feeding DNOM to laying hens produced dose-dependent enrichments of DHA in their eggs, liver, and muscles by regulating key genes involved in the elongation and desaturation of polyunsaturated fatty acids. Our findings will help produce DHA-enriched eggs.