Although docosahexaenoic acid ( DHA ) enrichment in eggs has been extensively studied in laying hens, research on DHA-fortified eggs in quails remains limited. This study evaluated the effects of graded levels of Schizochytrium algae powder ( SAP ) on production performance, egg quality, egg DHA enrichment and fatty acid composition, and related gene expression responsible for DHA absorption and transport in yellow-feathered laying quails. A total of 960 birds were randomly assigned to four dietary groups (0%, 0.4%, 0.8%, or 1.2% SAP) for an eight-week trial, with each group consisting of six replicates of forty quails each. A quadratic response was observed for egg production and egg mass ( P < 0.05), with the 0.4% SAP group higher than the control group ( P < 0.05). A significant decreasing linear trend in mortality was observed with increasing SAP levels ( P < 0.05). Egg yolk color responded linearly and quadratically to dietary SAP at both 4 and 8 weeks ( P < 0.05), with all supplemented groups exhibiting higher values than the control ( P < 0.05). DHA content in whole egg and yolk exhibited linear and quadratic increases with SAP supplementation at all timepoints ( P < 0.05), resulting in higher levels than the control in all SAP-treated groups ( P < 0.05) and plateauing at the 0.8% inclusion level. Moreover, SAP supplementation linearly elevated total omega-3 polyunsaturated fatty acid content and the omega-3/omega-6 ratio, while linearly reducing γ-linolenic acid and arachidonic acid concentrations in yolk ( P < 0.05). Transcriptional analysis revealed linear upregulation of key genes involved in DHA absorption and transport in the duodenum, jejunum, and liver in response to SAP supplementation ( P < 0.05). These findings demonstrate that dietary supplementation with SAP quadratically increased production performance, improved yolk color, enriched egg DHA content, elevated the omega-3/omega-6 ratio, and modulated the expression of genes involved in DHA absorption and transport. Collectively, this study provides an effective strategy for developing DHA-enriched quail eggs, with an optimal dietary SAP inclusion range of 0.4%–0.8%.
Qin et al. (Sun,) studied this question.