Effects of seasonal changes in food quality and food intake on the transport of sodium and butyrate across ruminal epithelium of reindeer.

Transport of 22Na and 14C-butyrate across the ruminal epithelium of captive reindeer fed a concentrate diet in summer (n=5) and in winter (n=5) and from free-ranging reindeer taken from summer (n=3) and winter pasture (n=5) was measured in vitro in Ussing chambers. Significant amounts of both Na+ and butyrate were transported across the isolated epithelium without any external driving force. The ruminal transport of Na+ and butyrate were interacting, as evidenced by both the observed amiloride-induced reduction of net butyrate-transport and by the positive correlation between net transport of butyrate and Na+.

Transport of butyrate across the isolated bovine rumen epithelium--interaction with sodium, chloride and bicarbonate.

The Ussing chamber technique was used for studying unidirectional fluxes of 14C-butyrate across the bovine rumen epithelium in vitro. Significant amounts of butyrate were absorbed across the bovine rumen epithelium in vitro, without any external driving force. The paracellular pathway was quantitatively insignificant.

Ruminal transport and metabolism of short-chain fatty acids (SCFA) in vitro: effect of SCFA chain length and pH.

The unidirectional transport and metabolism of 14C-labeled acetate, propionate and butyrate across the isolated bovine rumen epithelium was measured in vitro by the Ussing chamber technique. There was a significant, but relatively small, net secretion of acetate and propionate, and a large and significant net absorption of butyrate. The results demonstrate that the mucosal-serosal (MS) pathway for short-chain fatty acids (SCFA) is different from the serosal-mucosal (SM) pathway, and that butyrate is treated differently from acetate and propionate by the epithelium.

Absorption and fate of L- and D-lactic acid in ruminants.

Lactic acid is produced in significant amounts in the rumen on rations rich in easily digestible carbohydrates such as starch and sugars. If high amounts of concentrates, containing starch and sugars, are fed to high lactating dairy cows, lactic acid concentrations in rumen fluid up to 80 mmol/l can be found. If such high concentrations of lactic acid are consistent during longer periods of time, rumen acidosis may arise, causing disfunction and necrosis of rumen epithelium.

Feed-induced changes in transport across the rumen epithelium.

The effect of feeding strategy on rumen epithelial growth and transport capacity were studied in sixteen dairy cows. There was a significant effect of feeding strategy on transport of butyrate, sodium and chloride ions, which could not be explained by changes in epithelial surface area, structure or resistance.