The whitetail is a ruminant. It has a four-chambered stomach that processes large quantities of low-nutrient foods. A deer can fill its stomach in one or two hours, depending on the abundance and type of vegetation or mast it eats. When a deer feeds, it tongues food to the back of its mouth and chews just enough to swallow. Food passes down the gullet and into the stomach.
Food then goes into the rumen, which can store 8 to 9 quarts. The rumen acts as a fermentation vat, and most digestion occurs in this area. Billions of microorganisms break down fibers, cellulose and other plant components and convert them into materials that can be used by the deer’s digestive system. The lining of the rumen has small spaghetti-like fringes called papillae. Over 40 percent of a deer’s energy is derived from the acids absorbed through the papillae and the walls of the rumen.
After a doe or buck fills its paunch, it lies down in a secluded place to chew its cud. After chewing its cud awhile, a deer re-swallows the food and it passes to the second portion of the stomach, or the reticulum. The reticulum has a lining that looks like a honeycomb. It holds food in clumps, which can grow to the size of softballs. The main function of the reticulum is to filter out any foreign material.
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After about 16 hours, food passes to the third chamber, the omasum, where intensive digestion and absorption take place. The omasum’s lining has 40 flaps of varying heights, which absorb most of the water from the food.
The last compartment, the abomasum, has a smooth, slippery lining with about 12 elongated folds. The abomasum produces acid to break down food pieces for easier absorption of nutrients.
Food eventually passes through a deer’s intestines, where most of the liquid is absorbed and undigested particles are left behind. These particles are passed as excrement. A deer urinates and defecates an average of 13 times a day.