Jiaxin Chen ¹ Siwei Wang ^1,2 Xuejiao Yin ³ Chunhui Duan ¹ Jinhui Li ¹ Yue-Qin Liu ¹ Yingjie Zhang ^1*

• ¹ Hebei Agricultural University, Baoding, China
• ² Institute of Grain and Oil Crops, Hebei Academy of Agricultural and Forestry Sciences, Shijiazhuang, Hebei Province, China
• ³ College of Animal Science and Technology, Hebei Normal University of Science and Technology, Qinhuangdao, Hebei Province, China

Pregnancy toxemia (PT) is a nutritional metabolic disease of ewes in late pregnancy. This study aimed to reveal the relationship between rumen microbiota and PT. We selected ten healthy ewes (CON) and ten pregnancy toxemia ewes (PT) at 135 day of gestation according to the blood β-hydroxybutyrate (BHBA), glucose (Glu) concentrations and clinical symptoms. Blood and rumen fluid were collected before morning feeding to determine serum biochemical indices and rumen fermentation parameters. Total DNA of rumen fluid was extracted and the V3-V4 regions of 16S rRNA were amplified by PCR for high-throughput sequencing. The results showed that the serum concentrations of Glu, total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), uric acid (UA), creatinine (Cr), acetate, propionate, butyrate, and microbial crude protein (MCP) were decreased (P<0.05) and the concentrations of BHBA, aspartate aminotransferase (AST), acetate to propionate ratio (A/P), and ammonia nitrogen (NH3-N) were higher (P<0.05) in PT ewes than those in CON ewes. 16S rRNA analysis showed the differences of β-diversity were observed in rumen microbiota between CON and PT ewes. At the phylum level, the relative abundance of Bacteroidota and Proteobacteria were higher (P<0.01), while Firmicutes was lower (P<0.01) in PT ewes. At the genus level, the relative abundance of Prevotella, Butyrivibrio, Ruminococcus, Lachnospiraceae_AC2044_group, Lachnospiraceae_XPB1014_group, Lachnospiraceae_ND3007_group, and Oribacterium were lower (P<0.01) in PT ewes. Meanwhile, the relative abundance of Oribacterium, Butyrivibrio, Ruminococcus, and Lachnospiraceae_AC2044_group were positively correlated (P<0.01) with Glu, INS, acetate, propionate, and butyrate, and negatively correlated (P<0.01) with BHBA, P, GC, AST, and A/P. In conclusion, the decrease of Oribacterium, Butyrivibrio, Ruminococcus, and Lachnospiraceae_AC2044_group in the rumen of PT ewes reduced the concentrations of volatile fatty acids (acetate, propionate, and butyrate) and serum Glu, and increased BHBA concentration, indicating that the differences in rumen bacteria genera were related to pregnancy toxemia of ewes.