Effects of weaning on regulators of volatile fatty acid absorption and intracellular pH in Holstein calves

Abstract

In calves, changes in intracellular pH regulation dynamics and volatile fatty acid (VFA) transporter abundance through the weaning transition have not previously been described. The proton exporter NHE3 decreases in abundance between the preweaning and postweaning phase. Preweaning, the bicarbonate importer NBC1 increases in abundance in calves fed milk only versus those fed milk and solid feed. With solid feed consumption, no changes in abundance for the VFA transporter MCT1 were observed preweaning or postweaning. Some short-chain fatty acids (SCFA) are still imported through passive diffusion. Highlights• Calves may experience dysregulation of intracellular pH through weaning.• VFA concentration changes in the rumen do not equate to VFA transporter abundance.• The calf rumen can handle large amounts of fermentable feed without negative effects.• Cell size and relative cell circumference change as the rumen is developing.