The gut microbiome and its role in the development and function of newborn calf gastrointestinal tract

Abstract Text:

Microbial colonization plays important roles in neonatal gut health. However, studies on gut microbial composition and how it can shape host function during early life in ruminants are limited. Here, we report some of our recent efforts on studying host-microbial interactions in neonatal calves focusing on small intestine collected from animals from soon after birth to 6 weeks of age. The use of molecular based approaches revealed extensive colonization of the gut with active microbiota during birth.  Composition of the newborn gut microbiota was significantly different from the maternal microbiota in the birth canal and the environmental microbiome. Further differences in diversity were observed between tissue-attached (epimural) and content-associated microbiomes. Epimural communities consisted primarily of Pseudomonadaceae and Propionibacteriaceae, whereas Propionibacteriaceae, Prevotellaceae, Ruminococcaceae and Lachnospiraceae dominated luminal contents. Within the first week of life, Veillonellaceae and Lachnospiraceace dominated epimural communities, while Bacteroidaceae, Clostridiaceae, and Lactobacillaceae dominated content communities. Investigation of calf small intestinal transcriptomes using RNA-seq revealed that the expression of immune-related genes at birth was different from three other developmental stages (week 1, 3 & 6) in jejunum and ileum. The expression of genes related to tight junction proteins, antimicrobial peptides, NOD-like receptors, regulatory T cell marker, and cytokines underwent dynamic changes within the first week of life along with the observed changes in microbiome. This suggests that the first week postpartum is a critical developmental period for intestinal epithelial barrier and development of the mucosal immune system may be responding to the changing microbial composition. This conclusion is supported by evidence of strong correlations between expression of mucosal immune-related genes and total bacterial population in different gut regions at different ages. This study provides evidence that establishment of the small intestinal-specific microbiota begins during birth and its composition deviates significantly from the dam’s microbiota. This process may be modulated primarily by host selection. The establishment of such “individualized” gut microbiota may be an important regulator of gut tissue and immune function development. Our findings provide fundamental knowledge regarding host-microbial interactions in neonatal calves and may support future development of more effective strategies to improve neonatal gut health.

Keywords: calf, gut health, mucosal immunity