Effect of Feeding High-Grain Restricted-Roughage Rations with and without Bicarbonates on the Fat Content of Milk Produced and Proportions of Volatile Fatty Acids in the Rumen

Abstract

Lactating dairy cows were fed rations high in grain (34#/cow/day), low in roughage (5,#cow/day), supplemented with and without bicarbonates (Na and K equal parts). The bicarbonate was mixed into the grain mixture at 2 levels 1.5% and 3.0%. It was found that bicarbonate feeding prevented and/or corrected the production of low-fat milk under these conditons of feeding. A study of the rumen volatile fatty acids revealed that the supplemental bicarbonate functioned in the rumen to cause a change in the proportions of the acids produced. The molar proportions of the volatile acids in the rumen of the cows fed bicarbonates approximated those found in the rumen of cows fed normal rations; whereas the volatile acids in the rumen of the cows fed high grain without bicarbonates showed significantly higher levels of propionic acid.