Concentrations of Volatile Fatty Acids and Lactic Acid in the Rumen as Influenced by Diet and Post-Feeding Time

The concentration and the percentage of individual volatile fatty acids and the concentration of lactic acid was determined in the rumen fluid of rumen-fistulated cattle at 15 intervals after feeding. Diets consisted of long alfalfa hay, dehydrated alfalfa pellets, flaked corn, rolled barley, dried beet pulp, rolled milo, cracked corn and corn silage, and flaked corn and corn silage. An acetic: propionic acid ratio similar to that for hay was produced by dried beet pulp or milo. Flaked corn produced a lower ratio than cracked corn but more lactic acid when both were fed with corn silage. Dried beet pulp resulted in the highest lactic acid levels (73 mg %). The possible significance of ruminal lactate levels to milk-fat depression is discussed.