The gastrointestinal tract (GIT) of cattle is an incredibly complex organ system, composed of structural and immune cells, as well as its associated microbiome. While digestion-related functions are well-documented, recent research has highlighted the GIT's systemic influence on immune function. This has led to the concept of 'gut health' becoming more prevalent in both human and animal health discussions. However, there is still much to uncover about the characteristics of a typical or 'healthy' GIT in feedlot cattle.
GIT health is directly linked to the ability to digest and absorb nutrients while maintaining a barrier function, allowing beneficial substances like nutrients to pass through while preventing harmful pathogens. This barrier function is intricately tied to the integrity of the tissue, which is influenced by tight junction proteins (TJPs) and the gastrointestinal microbiome.
Tight junctions, or gap junctions, are microscopic spaces between intestinal epithelial cells that regulate the passage of molecules across the epithelium. These junctions are formed by various protein families, including claudin, occludin, zona occludin, and cadherin. The functions of these individual proteins are complex, with some promoting connectivity between cells and others promoting leakiness. Several TJPs are complementary, providing redundancy in their function. Additionally, because TJPs are host-derived, they are influenced by luminal contents and the microbiome.
The microbiome of cattle has long been recognized as a key factor in overall health. While the rumen and fecal microbiomes have been well-characterized, the microbiota found in other GIT sites remains less understood. Furthermore, many studies have focused on young calves or lactating dairy cows, with fewer investigations into the microbiomes of finish-fed beef animals produced in typical North American production systems.
Given the annual feeding of approximately 25 million cattle in the United States, with around 6 million in the Southern Plains alone, there is a growing impetus to use feed supplements to modify the microbiome for potential health benefits. However, there is a need to first characterize the core microbiome constituents and functions to provide a logical context for evaluating the utility of these products.
This study aimed to characterize the gastrointestinal microbiota and host tight junction protein (TJP) expression in clinically healthy, high-performing feedlot steers harvested in the Texas Panhandle. Specifically, the researchers sought to describe the composition and core members of microbial communities at distinct GIT sites (rumen, jejunum, and colon), and to quantify both protein and gene expression of select TJPs within corresponding tissues.
