The effect of adding different proportions of black wolfberry residues to the diet on the production performance, egg quality and fecal microorganisms of laying hens.

The present study investigated the impacts of adding varying proportions of black wolfberry residues to the diet on the production performance, egg quality, and intestinal health of Hy-Line Brown laying hens. A total of 600 healthy 20‑week‑old hens were randomly allocated to three groups (10 replicates/group, 20 hens/replicate) and fed either a basal diet (CK) or a basal diet supplemented with 1.0% (T1) or 1.5% (T2) black wolfberry residues for 60 days. Measurements included growth performance (feed intake, egg production, feed conversion ratio), egg quality (yolk color, Haugh unit, eggshell strength), egg nutrients (amino acids, total cholesterol, minerals Na, P, Ca, Fe, Zn, Se, and vitamins VA, VD₃, VE, VB₂, VB₉), fatty acid profile, and cecal microbiota (16S rRNA sequencing). The results showed that black wolfberry residues significantly increased average daily feed intake (P < 0.01). In the T2 group, yolk color and total amino acid content in eggs significantly increased (P < 0.01), while total cholesterol content significantly decreased (P < 0.01). At 30 days, compared with the CK group, the T1 group increased the contents of P, Ca, Fe, Zn, Se and VB2, decreased the Na content in eggs (P < 0.01). Meanwhile the T2 group increased the contents of Na, P, K, and Se in eggs (P < 0.01). At 60 days, both test groups had significantly increased Na and K contents (P < 0.01), but significantly decreased P, Ca, Fe, Zn, and VD3 contents in eggs (P < 0.01). Compared with the CK group, the T1 group showed significantly increased methyl oleate content and decreased levels of palmitic acid, stearic acid, linoleic acid, and arachidonic acid in eggs at all measured time points. In contrast, the T2 group elevated both methyl oleate and DHA contents, while reducing the levels of myristic acid, palmitic acid, stearic acid, and arachidonic acid in eggs. 16S rRNA sequencing analysis indicated that adding black wolfberry residues enhanced the richness of Firmicutes and Bacteroidetes, and reduced the relative abundance of Fusobacteria. In conclusion, dietary supplementation with black wolfberry residues, particularly at 1.5%, improved egg quality by increasing yolk color, total amino acids, DHA, and minerals (Se, Zn) while reducing total cholesterol. These changes suggest enhanced antioxidant capacity and potential nutritional benefits for consumers, such as improved dietary intake of essential micronutrients. Furthermore, modulation of cecal microbiota (increased beneficial Romboutsia, decreased Fusobacterium) may contribute to the observed effects on egg composition.