The effects of artificially dosed adult rumen contents on abomasum transcriptome and associated microbial community structure in calves

Authors: NARENGAOWA, FNU - China Agriculture University; Li, Wenli; MURPHY, BRIANNA - University Of Wisconsin; COX, MADISON - University Of Wisconsin; SUEN, GARRET - University Of Wisconsin

Submitted to: Genes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/9/2021
Publication Date: 3/16/2021
Citation: Narengaowa, F., Li, W., Murphy, B., Cox, M., Suen, G. 2021. The effects of artificially dosed adult rumen contents on abomasum transcriptome and associated microbial community structure in calves. Genes. 12(3). Article 424. https://doi.org/10.3390/genes12030424.
DOI: https://doi.org/10.3390/genes12030424

Interpretive Summary: Artificial dosing of adult ruminal contents might be an efficient way to help microbial colonization of the rumen in neonatal cattle. This study aimed at examing the changes in the transcriptional profile in the true stomach and microbial community in young calves after such dosing. Four young bull calves were randomly dosed with freshly extracted rumen contents from an adult cow (HE, n=4), or sterilized ruminal contents (Con, n=4). The inocula were administered within 3 days of birth, then 2, 4, and 6 weeks following the initial dosing. Abomasum tissues were collected immediately after sacrifice at 8 weeks of age. Total RNA sequencing was used to assess the abomasal microbial community and gene expression in the abomasum. Our study provided a transcriptome level understanding of the molecular mechanisms in the abomasum of young calves dosed with rumen contents collected from adult cows. Knowledge gained through this study could fill gaps in understanding of the abomasum in young calves at the molecular level, especially their transcriptome changes after early inoculation of ruminal contents.

Technical Abstract: Artificial dosing of adult ruminal contents might be an efficient way to help microbial colonization of the rumen in neonatal cattle. This study aimed at elucidating the changes in abomasum transcriptional profile and microbial community in young calves after such dosing. Four young bull calves were randomly dosed with freshly extracted ruminal contents from an adult cow (HE, n=4), or sterilized ruminal contents (Con, n=4). The inoculum was administered within 3 days of birth, then 2, 4, and 6 weeks following the initial dosing. Abomasum tissues were collected immediately after sacrifice at 8 weeks of age. Total RNA sequencing was used to assess the abomasal microbial community and gene expression changes in the abomasum between the Con and HE groups. Raw reads were mapped to cattle reference genome (Bos taurus UMD 3.1) with STAR (2.5.2b) and gene expression analysis was done using DEseq2. After genus-level classification using Kraken2, Kruskal-Wallis test indicated that 5 genera (Tannerella, Desulfovibrio, Deinococcus, Leptotrichia, and Eubacterium; P < 0.05) showed significant difference in abundance between the treatments. A total of 348 up-regulated genes (URG) and 627 down-regulated genes (DRG) were identified in HE group compared to control (P < 0.05, fold-change > 1.5, mean readcounts > 5). Pathway analysis indicated that URGs were involved in immune system processes (GO:0002376; 26 genes, P «0.00001) and defense responses to viruses (GO:0051607; 15 genes, P «0.00001), while the DRG were involved in ion transport (GO:0006811; 46 genes, P «0.00001), ATP biosynthesis (GO:0006754; 12 genes, P «0.00001), and mitochondrial electron transport (GO:0006122; 10 genes, P «0.00001). Moreover, correlation analysis indicated that Desulfovibrio, which was significantly higher in HE group, was positively related to the TRPM4 gene (r > 0.7, P < 0.05), which has a reported role related to immune system development. Overall, our study provided insights into the molecular changes in the abomasum in young calves after dosing of ruminal contents.