Copper intake influences offspring growth, Cu excretion, microbiota, and antibiotic resistance genes via vertical transmission in pigeons

Copper (Cu) improves pigeon growth; however, excessive dietary Cu in breeding pigeons (BP) ultimately harms the health of squab pigeons (SP). In order to explore the influence of different doses of Cu in BP, and its effects on the metabolism, intestinal microbiota and the transmission of antibiotic-resistant genes (ARGs) in SP through vertical transmission, this study analyzed the effects of varying Cu doses on BP milk microbiota, along with serum and fecal Cu content, intestinal microbiota composition, and ARGs in SP. The findings revealed that sufficient Cu improved the average daily feed intake of BP. Dietary Cu supplementation affected its content in BP milk, serum, and feces, as well as Cu content in SP serum and feces. Importantly, Cu significantly altered the microbiota composition in BP milk, and ileum microbiota was reshaped in SP correspondingly. Furthermore, Cu markedly increased ARGs in SP, particularly in the T16 treatment group (basal diet supplemented with 16 mg/kg Cu), where higher abundances of arlR , cdeA , dfrL , efrA , optrA , and lsaE were observed. Correlation analysis showed that Lactobacillus and Escherichia-Shigella in BP milk were negatively and positively associated with Streptococcus and Clostridium in SP ileal mucosa samples, respectively. Diets supplemented with 16 mg/kg Cu led to the highest abundance of Gallibacterium in BP milk, which was positively linked to cdeA , lsaE , and optrA in SP. Overall, this research reveals the effects of dietary Cu levels on BP milk, Cu absorption and excretion, and its influence on SP microbiota and ARGs through vertical transmission. • Cu contents in SP serum and feces were strongly correlated with Cu content in BP milk across different dietary Cu doses. • Dietary Cu supplementation affected the microbiota of BP, which was subsequently transmitted to SP via vertical transmission. • Higher dietary Cu levels markedly increased the abundance of ARGs in SP.