Breed Differences In The Expression Levels Of Gga-Mir-222a In Laying Hens Influenced H2S Production By Regulating Methionine Synthase Genes In Gut Bacteria

Abstract Background: The microbiota in the cecum of laying hens was critical for host digestion metabolism and odor gas production. Recent studies have suggested that host miRNAs could regulate gene expression in the gut microbiota. The expression profiles of host-derived miRNAs in the cecal content of two laying hen breeds, Hy-line Gray and Lohmann Pink, which have dissimilar H2S production were characterized, and their possible effects on H2S production by regulating the expression of related genes in the microbiota were demonstrated. Results: The differential expression of microbial serine O-acetyltransferase, methionine synthase, aspartate aminotransferase, methionine-gamma-lyase and adenylylsulfate kinase between the two breeds resulted in lower H2S production in the Hy-line hens. The results also demonstrated miRNA exosomes in the cecal content of laying hens and the potential miRNA-target relationships between 9 differentially expressed miRNAs and 9 differentially expressed microbial genes related to H2S production were investigated, among which gga-miR-222a targeted two methionine synthase genes, Odosp_3416 and BF9343_2953. An in vitro fermentation experiment showed that gga-miR-222a upregulated the expression of these genes, which increased methionine concentrations but decreased H2S production and soluble sulfide concentrations, indicating the potential of host-derived gga-miR-222a to reduce H2S emission in laying hens. Conclusion: These findings identify both a physiologic role by which miRNA shapes the cecal microbiota of laying hens and a strategy to use host miRNAs to manipulate the microbiome and actively expressed key microbial genes to reduce H2S emission and breed environmentally friendly laying hens.