Multiomics-based analysis of key genes, metabolites and pathways unveils mechanism associated with social rank in Chickens.

Social rank plays a crucial role in shaping physiological, psychological and immune responses in animals. Our previous study found that gut microbes and short-chain fatty acids as well as brain neurotransmitters are involved with the mechanism of social hierarchy. Nevertheless, how these gut and brain metabolites interact to affect the mechanism of social hierarchy in chickens is not yet known. In this study, 40 hens were randomly divided into four groups at the age of 49 days, and social rank of each hen was determined by 6 times according to the feeding competition tests. Then hens ranked 1/2 were named High Social Rank (HSR, n = 8) and hens ranked 9/10 were named Low Social Rank (LSR, n = 8). We use multiomics to explore gut metabolites, neurotransmitters, and brain transcriptome, neurotransmitters and related gene expression in 91-day-old chickens, so as to better understand the underpinning mechanism that regulates the social hierarchy. We found that the pro-inflammatory genes were significantly lower while anti-inflammatory factor in spleen was higher in HSR chickens than in LSR chickens (P<0.05). Besides, seven immune-related genes were significantly different in the amygdala between HSR and LSR (P < 0.05). In addition, AVP, RXFP3, VIP and NKX2-1 were associated with the social rank through GABAergic neurons and neuroactive ligand-receptor pathways, with the up-regulation of 5-HT in the amygdala of LSR. Genes SLC11A2 and HMOX1 in ferroptosis pathway influenced the cecum metabolite l-glutamate and tyrosine. While fumaric, l-glutamic and 4-Oxoproline were found enriched in "alanine, aspartate and glutamate metabolism" and "arginine biosynthesis". In conclusion, social rank affects the immunity, in which higher ranking hens show better anti-inflammatory and lower pro-inflammatory than lower ranking hens. Genes TAP2, PLD4, P2RX7, ALDH9A1, SLC11A2, ADM, C3, AVP, RXFP3, VIP, NKX2-1, SLC11A2 and HMOX1 may play an important regulatory role on GABAergic neurons, neuroactive ligand-receptor and ferroptosis pathways related to neuron, immune, and stress behaviour, and in turn affects social rank. Fumaric, l-glutamic and 4-Oxoproline, may regulate social rank through the "alanine, aspartate and glutamate metabolism" and "arginine biosynthesis".