Particle Size and Effective Fiber in Dairy Cow Diets

Limited chewing takes place when a cow grazes or eats chopped forage, and a more thorough mastication will occur later when she “chews her cud.” Rumination, of which cud chewing is a part, is the process by which the contents of the rumen (the first chamber of the stomach) are thoroughly mixed and where the larger, less digested particles are redirected upward, to be regurgitated, chewed, and swallowed again. This process is repeated over and over until the feed particles attain a small enough size with relatively greater surface areas that enable bacteria and protozoa in the rumen to more efficiently feed and digest the particles. In time the feed leaves the reticulo-rumen and enters the omasum, on its way to the true stomach, the abomasum