Changes of serum metabolites and intestinal microflora structure in laying hens before and after fasting

<bold>Objective</bold> This study aims to explore the changes of serum metabolites and intestinal flora structure of laying hens before and after fasting，thus revealing the strategies of laying hens to cope with energy deficiency，and providing a theoretical basis for improving the feeding method of poultry and formulating scientific dietary formulations. <bold>Method</bold> A total of 90 252-day-old Hyline brown laying hens were randomly divided into three groups：control group（C），fasting group for 1 day（F1）and fasting group for 3 days（F3）with 6 replicates in each group and 5 chickens in each replicate.After the experiment，1 chicken was randomly selected from each replicate for slaughter.Blood and cecum contents were collected for serum non-targeted metabolome and 16S rDNA sequencing analysis. <bold>Result</bold> （1）The results of serum non-targeted metabolomics showed that after fasting，the levels of serum differential metabolites of laying hens increased，and the main differential metabolites were 1-methylhistidine，pipecolic acid，L-lysine，pantothenic acid，pyridoxamine，deoxycholic acid，dulcitol and acetyl-L-carnitine.That indicated that muscle protein decomposition and ketogenic reaction were enhanced after fasting in order to maintain the energy demand of the body.（2）The results of 16S rDNA sequencing of intestinal flora showed that after fasting，the intestinal flora diversity of laying hens showed a decreasing trend，and the flora structure changed significantly.The differentially dominant bacterial groups at the genus level included <italic>Rikenellaceae_RC9_gut_group</italic>，<italic>Bacteroides</italic>，<italic>Ruminococcus</italic>_<italic>torques_group</italic> and <italic>Desulfovibrio</italic>，etc.，all of which were related to energy metabolism.（3）Correlation analysis between differential dominant bacteria and differential metabolites showed that the abundance of bacteria was negatively correlated with the levels of deoxycholic acid and dulcitol，and positively correlated with the levels of other screened differential metabolites. <bold>Conclusion</bold> After fasting for 1 and 3 days，serum metabolites levels and intestinal microbes of laying hens change significantly，and the changes of different metabolites may be related to the changes of intestinal flora，and they jointly maintain metabolic homeostasis of laying hens.