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Adaptive Response of the Bovine Rumen Epithelium to Dietary Changes

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Title: Adaptive Response of the Bovine Rumen Epithelium to Dietary Changes
Author: Laarman, Anne Hermen
Department: Department of Animal and Poultry Science
Program: Animal and Poultry Science
Advisor: McBride, Brian W.
Abstract: This thesis studied the short-term and long-term adaptive response of the bovine rumen epithelium to dietary changes, and the impact of butyrate on the epithelium adaptive response. To study the short-term adaptive response, Holstein steers were switched from an ad libitum diet to either a subacute ruminal acidosis (SARA) challenge or a feed restriction treatment, and then acetate and butyrate fluxes through different short chain fatty acid (SCFA) transport mechanisms were measured in Ussing Chambers. Using immunofluorescence, we studied the long-term adaptive response by measuring temporal changes in SCFA transport capacity and intracellular pH regulation in rumen papillae over the transition period in Holstein dairy cows. Lastly, we investigated butyrate’s potential to influence the adaptive response by adding butyrate to the rumen during SARA in early lactating cows. In the first study, 5 d feed restriction increased butyrate flux via an upregulation of monocarboxylate co-transporter isoform 1, a basolateral SCFA transporter in the rumen epithelium. In the long-term response study, the transition period increased SCFA absorption capacity through epithelial remodeling and increased absorptive surface area, evidenced by decreased abundance of carbonic anhydrase 2. Due to a maintenance of SCFA transporters concurrent with an increase in absorptive surface area, SCFA absorption capacity increased. In the last study, butyrate augmented the SCFA absorption capacity during SARA by increasing monocarboxylate co-transporter 1 expression, and improving epithelial barrier integrity by increasing expression of genes associated with glycolysis and oxidative phosphorylation, while decreasing expression of lipogenic genes. Together, these studies show that the adaptive response of the rumen epithelium involves a short-term cellular response and a long-term morphological response that increase SCFA absorption capacity. The cellular response increases monocarboxylate co-transporter isoform 1 abundance, which can be augmented by supplying supplemental butyrate to the rumen. The morphological response increases absorptive surface area through epithelial remodeling. Epithelial remodeling can be improved by butyrate because butyrate induces a genomic shift to mob ilize energy and thus help maintain epithelial barrier integrity. Both the cellular adaptive response and the morphological adaptive response are dependent on key molecular factors that serve to modulate SCFA absorption in dairy cows during dietary transitions.
URI: http://hdl.handle.net/10214/8777
Date: 2015-04
Rights: Attribution-NonCommercial-NoDerivs 2.5 Canada


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