Relationship between Rumen Microbial Differences and Phenotype Traits among Hu Sheep and Crossbred Offspring Sheep.

Simple Summary: Simple Summary: The rumen is the most important digestive organ of ruminants, and its rich microbial co−evolved with the host to play a crucial role in immunomodulation, defense, digestive metabolism, animal productivity, and meat quality control. It also forms a complex regulatory network with host genes and phenotypes that are involved in maintaining organismal homeostasis. In this study, we compared the differences in rumen microorganisms between crossbred progeny of sheep and Hu sheep, identified key biomarkers, and analyzed their relationship with rumen function. The results showed that microbial diversity was significantly higher in crossbred progeny, which was able to alter the microbial community structure to regulate rumen fermentation, promote carbon homeostasis, and enhance amino acid metabolism. In addition, there were significant correlations between biomarkers and key traits. Therefore, we suggest that there is a link between sheep rumen microbes and differential traits in crossbred progeny, which provides new insights for sheep trait improvement. This experiment was conducted to investigate the effect of three–way hybrid sheep and Hu sheep on serum indicators, rumen fermentation, rumen enzyme activity, and microorganisms in sheep. Healthy and similar birth weights from three groups (Hu, n = 11; Charolais × Australian White × Hu, CAH, n = 11; Charolais × Dorper × Hu, CDH, n = 11) were selected to be fed by the ewes until 45 days of age. Subsequently, they were weaned intensively and underwent short–term fattening for 3 months along with selected male lambs fed intensively. During this period, they were fed and watered ad libitum. Blood and rumen fluid were collected and analyzed for serum indicators and rumen fluid microorganisms, enzyme activity, and VFA, respectively, at the end of the fattening period. Compared with Hu lamb, the offspring of the three–way hybrid lamb showed significant improvements in body weight, serum lactate dehydrogenase, and creatinine content. However, there was no significant effect on serum immunity and antioxidant indices. In addition, the rumen fluid volatile fatty acid (VFA) molar concentration and microcrystalline cellulose and lipase content were significantly lower in the three–way hybrid lamb compared to Hu lamb, but β–glucosidase, amylase, pepsin, and VFA molar ratio were not significantly affected. Subsequently, 16S rRNA sequencing diversity analysis revealed that three–way hybrid lamb significantly increased rumen microbial ACE and Chao1 indices compared to Hu lamb. Meanwhile, the abundance of Verrucomicrobiota and Synergistota significantly increased at the phylum level. Correlation analysis showed that Prevotella had the highest proportion, while Rikenellaceae_RC9_gut_group correlated most closely with others genus. The microbial communities isovaleric acid molar concentration and proportion were strongly correlated. In addition, there were significant differences in correlations between microbial communities and isobutyric acid, butyric acid and valeric acid content, and their molar proportion, but they were not significantly correlated with digestive enzymes. From the functional enrichment analysis, it was found that hybrid progeny were mainly enriched in the pyruvate metabolism, microbial metabolism in diverse environments, carbon metabolism, and quorum sensing pathways. In contrast, the Hu sheep were primarily enriched in the cysteine and methionine, amino sugar and nucleotide sugar, and biosynthesis of secondary metabolite pathways. These results suggest that hybridization can play a role in regulating organismal metabolism and improve animal production performance by influencing the structure and characteristics of microbial communities. [ABSTRACT FROM AUTHOR]