Rosemary extract improves egg quality by altering gut barrier function, intestinal microbiota, and oviductal gene expressions in late-phase laying hens

Background: Rosemary extract (RE) has been reported to exert antioxidant property. However, the application of RE in late-phase laying hens on egg quality, intestinal barrier and microbiota, and oviductal function has not been systematically studied. This study was investigated to detect the potential effects of RE on performance, egg quality, serum parameters, intestinal heath, cecal microbiota and metabolism, and oviductal gene expressions in late-phase laying hens. A total of 210 65-week-old “Jing Tint 6” laying hens were divided into five treatments and fed basal diet (control) or basal diet supplemented with chlortetracycline at 50 mg/kg or RE at 50, 100, and 200 mg/kg. Results: Our results showed that RE improved Haugh unit and n-6/n-3 of egg yolk, serum superoxide dismutase (SOD) and jejunal ZO-1 and Occludin, and decreased serum interleukin-6 (IL-6) and total cholesterol (TC). The biomarkers of cecal microbiota induced by RE, including Firmicutes, Eisenbergiella , Paraprevotella , Papillibacter , and butyrate were closely associated with Haugh unit, n-6/n-3, SOD, IL-6, and TC. PICRUSt2 analysis indicated that RE altered carbohydrate and amino acid metabolism of cecal microbiota and increased butyrate synthesizing enzymes, including 3-oxoacid CoA-transferase and butyrate-acetoacetate CoA-transferase. Moreover, transcriptomic analysis revealed that RE improved gene expressions and functional pathways related to immunity and albumen formation in the oviductal magnum. Conclusions: RE could increase egg quality of late-phase laying hens via modulating intestinal barrier, cecal microbiota and metabolism, and oviductal function. Overall, RE has the potential to use as an alternative to antibiotics to enhance egg quality of hens in the late phase of production.