The Remarkable Stomach of the Cow

The stomach of the cow is a remarkable organ. It has four compartments (rumen, reticulum, omasum, and abomasum), each designed to perform certain functions. By having this stomach, the cow is able to digest and efficiently use feedstuffs that humans and non-ruminant animals, such as the pig and chicken, cannot use. Examples of these feedstuffs include cellulose, which is used for energy, and urea, which is used to make protein.

When a calf is born the forestomach compartments (rumen, reticulum and omasum) are not developed, therefore the calf is unable to utilize dry feed. Development includes growth in size and musculature, growth of the papillae of the mucosal (inner) surface to provide for absorption of end products of digestion, and establishment of the microorganisms (bacteria, protozoa, fungi, etc.) that are responsible for digesting the feedstuffs. This development occurs only if dry feed is consumed, otherwise the forestomach compartments remain small and undeveloped.

Because dry feed cannot be used by the very young calf, it depends on milk for nutrition. As the calf grows it eats a small amount of dry feed at first, then consumes increasingly larger amounts, and the proportion of nutrients from milk decreases.

The nutrients in milk are digested in the fourth stomach compartment (abomasum) and intestines, and it would not be desirable for milk to go into the forestomach. To make it possible for dry feed to go into the rumen but for milk to go into the abomasum the calf has what is called the esophageal groove. This groove is actually two folds of tissue that can be brought together to form a tube. When the calf drinks milk a reflex action closes the folds to form a tube which conducts the milk from the end of the esophagus to the abomasum. When the calf eats dry feed the groove does not close and the dry feed is directed into the rumen and reticulum.

The above description is actually an over simplification of a complex system and series of events that take place. It should be obvious that this system was designed by an all wise Creator and did not happen by chance. (Editor's Note: Morrill was on the faculty at Kansas State University for thirty-three years and was involved in research that established some of the facts in the above article.)

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