Development and physiology of the rumen and the lower gut: Targets for improving gut health

Abstract

The gastrointestinal epithelium of the dairy cow and calf faces the challenge of protecting the host from the contents of the luminal milieu while controlling the absorption and metabolism of nutrients. Adaptations of the gastrointestinal tract play an important role in animal energetics as the portal-drained viscera accounts for 20% of the total oxygen consumption of the ruminant. The mechanisms that govern growth and barrier function of the gastrointestinal epithelium have received particular attention over the past decade, especially with advancements in molecular-based techniques, such as microarrays and next-generation DNA sequencing. The rumen has been the focal point of dairy cow and calf nutritional physiology research, whereas the lower gut has received less attention. Three key areas that require discovery-based and applied research include (1) early-life intestinal gut barrier function and growth; (2) how the weaning transition affects function of the rumen and intestine; and (3) gastrointestinal adaptations during the transition to high-energy diets in early lactation. In dairy nutrition, nutrients are seen not only as metabolic substrates, but also as signals that can alter gastrointestinal growth and barrier function. Nutrients have been shown to affect epithelial cell gene expression directly and, in concert with insulin-like growth factor, growth hormone, and glucagon-like peptide 2, play a pivotal role in gut tissue growth. The latest research suggests that ruminal and intestinal barrier function is compromised during the preweaning phase, at weaning, and in early lactation. Gastrointestinal barrier function is influenced by the presence of metabolites, such as butyrate, the resident microbiota, and the microbes provided in feed. In the first studies that investigated barrier function in cows and calves, it was determined that the expression of genes encoding tight junction proteins, such as claudins, occludins, and desmosomal cadherins, are affected by age and diet. Recent evidence suggests that the upper and lower gut can communicate, but the exact mechanisms of gastrointestinal cross-talk in ruminants have not been studied in detail. A deeper understanding of how diet and microbiota can affect growth and barrier function of the intestinal tract may facilitate the development of specific management regimens that could effectively influence gut function.

Microbial succession in the gastrointestinal tract of dairy cows from 2 weeks to first lactation

“…Most of these OTUs were saccharolytic genera including Lactobacillus and butyrate-producing Faecalibacterium 31. Given that butyrate promotes ruminal and intestinal development in calves32, these bacteria likely aid in GIT development but are then out-competed by fiber-degraders in older animals. Similar trends have been seen previously for Faecalibacterium 111216 and Lactobacillus 1112 in calf feces, which highlights their general importance at this stage.…”

Oral administration of propionic acid during lactation enhances the colonic barrier function

“…During lactation, individuals are susceptible to intestinal diseases, such as necrotizing enterocolitis, because the intestinal mucosal barrier has not yet matured and there is a lack of resistance to various stressors [14]. Therefore, pre-weaning male Sprague-Dawley rats 7 days after birth, which simulated the neonatal period in humans, were used as models in our research.…”

“…Consequently, the potential effects of propionic acid have long been underestimated [13]. In addition, pre-weaning is a special period in which the intestinal mucosal barrier has not yet matured, which results in the lack of resistance to various stresses [14]. Therefore, the pre-weaning rats were given an oral 2 mL/10 g of 200 mM propionic acid solution by gavage, and our study demonstrated that the oral administration of propionic acid during lactation increased its concentration in the proximal colon and enhanced epithelial barrier function.…”

Review: Utilization of yeast of Saccharomyces cerevisiae origin in artificially raised calves

“…Continued research on the effects of nutrients on gut development is paramount to understanding specific calf management strategies that can be put in place to enhance calf gut health and hence performance [89]. Microbial colonization is fundamental for the growth, development and function of the rumen [73] and is dependent on the diet [82].…”