This study evaluated the effects of kaempferol (KAE), and vitamin E (VE) on the performance, reproductive hormones, and the composition of the cecum and uterus microbiota in late-laying hens. A total of 192 49-week-old Jinghong No. 1 laying hens were randomly divided into four groups, with six replicates in each group and eight laying hens in each replicate, pre-reared for one week and formally tested for ten weeks. The CON group was fed basal diets, the VE group, the KAE group, and the KAE + VE group were fed a basal diet to which was added 0.2 g/kg VE, 0.4 g/kg KAE, and 0.2 g/kg VE + 0.4 g/kg KAE, respectively. The results are as follows. Compared to the CON group, the VE group, the KAE group, and the KAE + VE group significantly increased the egg production rate, average daily egg weight and significantly decreased the feed-to-egg ratio. The VE + KAE group significantly improved the Haugh unit. The VE group, the KAE group, and the KAE + VE group considerably enhanced the eggshell strength, eggshell relative weight, eggshell thickness, yolk color, and relative yolk weight. The serum E₂ and LH levels of the KAE group and the KAE + VE group and the serum FSH levels of the KAE + VE group were significantly higher. In the ovary, the KAE group and the KAE + VE group’s ESR1 gene expression levels were significantly higher, and the KAE + VE group’s FSHR gene expression levels were markedly higher. In the uterus, the KAE group and the KAE + VE group’s ESR1 gene expression levels were dramatically higher, and the KAE + VE group’s ESR2 and FSHR gene expression levels were significantly higher. 16S rRNA gene sequencing revealed a significant aggregation of cecum and uterus colonies in the Beta diversity PCoA. In the cecum, Firmicutes, Bacteroidetes, and WPS-2 were the dominant phylums. In the uterus, the Firmicutes, Proteobacteria, and Bacteroidetes were the dominant phylums. The KAE + VE group’s F/B was significantly higher at the phylum level than in the CON group and the VE group. In summary, the addition of VE and KAE to the diet can improve the production performance of late-laying hens, increase the content of reproductive hormones, and stabilize the cecal and uterus microbiota, which may be related to the hormone and microbiota linkage of the gut–uterus axis.

Dietary fiber raw materials for meat rabbits are diverse, yet the effects of their hydration properties and fermentation on growth performance and intestinal health remain insufficiently understood. In this study, we first systematically analyzed 12 commercial fiber raw materials for nutrient composition, hydration properties, and in vitro fermentation characteristics. Principal component analysis (PCA) was employed to reduce the dimensionality of the nutritional and physicochemical parameters, extracting two key dimensions: the first was predominantly defined by fiber fractions and viscosity, while the second was jointly driven by water binding capacity (WBC), water swelling capacity (WSC), gas production, and volatile fatty acid (VFA) generation. Subsequently, based on the similarity of fibers along the first principal component and their gradient distribution along the second, four representative fiber raw materials with graded hydration properties and fermentation were selected for in vivo validation: peanut vine meal (PV) < Pennisetum giganteum meal (PG) < Moringa oleifera leaf meal (MO) < mulberry leaf meal (ML). A total of 96 weaned New Zealand white rabbits were randomly assigned to four groups and fed diets containing PV, PG, MO, or ML, respectively, over a 35-day feeding trial. Growth performance, diarrhea incidence, intestinal morphology, cecal microbiota, and VFA profiles were evaluated. In vivo results showed that MO was associated with optimized cecal microbiota, increased short-chain fatty acids, and reduced diarrhea. In contrast, despite its high in vitro fermentation, ML was associated with intestinal inflammation, decreased short-chain fatty acids, reduced average daily gain and average daily feed intake, elevated branched-chain fatty acids and ammonia nitrogen, and increased diarrhea incidence. Correlation analysis further revealed that enriched Bacteroides was closely associated with reduced growth performance and impaired intestinal health. Collectively, these findings suggest that MO with moderate hydration properties and high fermentation may be more beneficial for optimizing growth performance and intestinal health in meat rabbits than ML with high fermentation alone. This study provides a reference for the rational selection of fiber resources in meat rabbit production.