ABSTRACT Our current project aims to elucidate the impact of advancing date on eggshell quality in Shanma ducks and its underlying mechanisms. A total of 60 healthy Shanma ducks from the youth group (160 days old) and the elderly group (560 days old) were selected to evaluate eggshell physicochemical properties, serum calcium and phosphorus metabolism, gut microbiota, and uterine tissue transcriptomic expressions. Results demonstrated that the elderly group exhibited significantly reduced eggshell thickness and strength, with ultrastructural analysis revealing uneven calcium deposition and a thinner effective layer compared to the youth group. Elderly ducks showed decreased serum levels of 1,25-dihydroxyvitamin D₃, alongside elevated parathyroid hormone and bone remodeling markers (TRAP-5b, BAP), suggesting disrupted calcium metabolism. Histological observation identified duodenal villus atrophy, humeral matrix erosion, and uterine interstitial edema in elderly ducks. Gut microbiome analysis indicated reduced microbial diversity and simplified community structure in elderly ducks, with Helicobacter and Lactobacillus becoming dominant genera, and significant downregulation of mineral absorption-related functional pathways. Uterine transcriptomics identified 607 differentially expressed genes, significantly enriched in pathways such as calcium signaling and steroid hormone biosynthesis. Correlation network analysis further revealed that eggshell strength was closely associated with bone resorption markers, Helicobacter abundance, and the expression of multiple calcium metabolism-related genes (e.g., KCNS2, GABRA1, FOXF1, ATP1B1 ). Notably, the positive correlation between eggshell strength and SMAD9 observed in the youth group was absent in the elderly group. In conclusion, the age-related decline in eggshell quality results from the combined effects of calcium metabolism imbalance, enhanced bone remodeling, gut microbial dysbiosis, and uterine functional disruption, providing multi-omics insights into the decline of avian reproductive performance with age.
Xiong et al. (2026) studied this question.