Rumen

When food enters a bovine’s stomach, it undergoes a process called enteric fermentation: microbes and bacteria partially break down the food particles, which then ferment in the part of the stomach called the rumen.

In the newborn ruminant the abomasum is about as large as the rumen and remains relatively large as long as only milk is consumed (Brugnone, 1809). As the young ruminant consumes forages, the reticulum, and particularly the rumen, develop rapidly.