A primary characteristic of the ruminant stomach is that the first three of the four compartments (rumen, reticulum and omasum) do not secrete a digestive juice. Extensive fermentative digestion results from large numbers of bacteria and protozoa in the first three compartments. Such fermentation precedes digestion by means of enzymes and hydrochloric acid secreted in the fourth compartment – the abomasum - and enzymes secreted in the intestine.

At birth the abomasum is the largest compartment of the ruminant stomach. However, as the newborn ruminant matures, it gradually increases intake of roughage, and the rumen reticulum and omasum grow rapidly and reach adult proportions at about 6-12 months of age. 

Since the first compartment, the rumen, is working at a neutral pH in the adult animal it doesn’t benefit from additional acid in the feed. The saliva contains sodium carbonate and is constantly buffering the feed.

                   Stomach of a calf                                          Stomach of a grown cow

But there are still some benefits from using acids in ruminant feed:

As a feed preservative - all animals benefit from a feed free from mould and bacteria.

As silage additive - acids and salts of organic acids are used as silage additives. They preserve grass and prolong storage stability.

Prevention of ketosis - when a cow is having a calf and is going from a dry period to produce milk, the energy requirement suddenly becomes very high. But energy uptake from the feed is limited and the blood sugar level decreases. As the amount of energy and calcium required are not available in the feed consumed, these can be provided by calcium propionate.

As a milk replacer - milk replacers can be acidified since the calf uses the abomasum and not the rumen. The acid is used as a feed preservative and to control the feed intake.

For more specific information about acidification or silage click on: acidification or silage.