Low Ruminal pH Reduces Dietary Fiber Digestion via Reduced Microbial Attachment

Microbial attachment and feed digestion in the rumen.

Direct microscopic examination of the rumen and its contents shows microbial populations largely attached to feed particles in the digesta. Most feeds contain a surface layer that is resistant to attachment and therefore to digestion. Infiltration of these recalcitrant epidermal layers through damage sites or through focused enzymatic attack is essential for initiation of the digestive process....

Effect of Ruminal pH Alteration on Digestion in Steers Fed a High Concentrate Diet

Mature Angus steers were intraruminally infused with base to increase ruminal pH. Base infusions, increasing rumen pH from 5.8 to 6.2, did not change duodenal pH but tended to reduce fecal pH. Increased ruminal pH tended to increase digestion of fiber (9 percent) but reduced ruminal digestion of starch by 18 percent (P> .05). Ruminal pH and ruminal starch digestion were negatively correlated (P...

Is Fiber Digestion in the Rumen Reduced by Catabolite Repression?

Short communication: Effect of subacute ruminal acidosis on in situ fiber digestion in lactating dairy cows.

Subacute ruminal acidosis (SARA) was induced by replacing 25% of the total mixed ration intake [dry matter (DM) basis] with pellets consisting of 50% wheat and 50% barley. This reduced dietary forage content (DM basis) from 39.7 to 29.8% and increased the dietary concentrate content from 60.3 to 70.2%. Induction of SARA reduced the 24- and 48-h in situ neutral detergent fiber (NDF) degradabilit...

Initial pH as a determinant of cellulose digestion rate by mixed ruminal microorganisms in vitro.

In vitro fermentations of pure cellulose by mixed ruminal microorganisms were conducted under conditions in which pH declined within ranges similar to those observed in the rumen. At low cellulose concentrations (12.5 g/L), the first-order rate constants (k) of cellulose disappearance were successively lower at initial pH values of 6.86, 6.56, and 6.02, but in each case the value of k was maint...