J. Daniel Young ^1,2 Lee J. Pinnell ² Cory A Wolfe ² Enrique Doster ² Robert Valeris-Chacin ² Ty E Lawrence ¹ John T. Richeson ¹ Paul S. Morley ^2*

• ¹ West Texas A&M University, Canyon, United States
• ² VERO Program, Texas A&M University, Canyon, Texas, United States

The gastrointestinal microbiota profoundly influences the health and productivity of animals. This study aimed to characterize microbial community structures of the mouth, gastrointestinal tract (GIT), and feces of cattle. Samples were collected from 18 Akaushi crossbred steers at harvest from multiple locations, including the oral cavity, rumen, abomasum, duodenum, jejunum, ileum, cecum, spiral colon, distal colon, and feces. These cattle were raised without exposure to antimicrobial drugs or hormone implants. Total microbial abundance was assessed using qPCR targeting the V3-V4 region of the 16S rRNA gene, and microbial community composition was evaluated through 16S rRNA gene sequencing. Total microbial abundance was lesser in the small intestine than in other GIT regions (P ≤ 0.05). Additionally, microbial communities in the small intestine had lower richness and diversity than other regions (P ≤ 0.05). Microbial community compositions were measurably different along the GIT, with greater relatedness in adjacent GIT sections when progressing from oral to aboral locations. communities of the entire GIT, which has important implications for future research.Additionally, examining microbiome data only at the phylum level likely oversimplifies important complexities of the microbial community structures, and investigations of lower taxonomic ranks should be included.