Glucose absorption, carbohydrase activities, and carbohydrate hydrolysis and uptake in the intestinal tract of mature sheep

Carbohydrates are the predominant source of energy used to carry out the biological processes of growth, maintenance, and reproduction in the animal body. Glucose is the most important carbohydrate metabolite in both the nonruminant and the ruminant animal. In the nonruminant, glucose is also the most abundant end product of carbohydrate digestion.

The nonruminant is able to utilize only traces of cellulose and hemicellulose as end products of microbial degradation in the large intestine, and the small intestine of this animal is the major site of carbohydrate assimilation. The microbiological digestion of carbohydrates makes the reticulo-rumen and to a lesser extent the omasum the major sites of carbohydrate assimilation in the ruminant animal. These microorganisms also degrade a portion of cellulose and hemicellulose to absorbable end products which can be utilized by the host animal.

The rumen, being the major site of carbohydrate assimilation, has received the greatest attention by investigators of protein, fat, and carbohydrate utilization in the ruminant. Some research has been conducted in an attempt to determine the ability of the preweaned ruminant to utilize certain carbohydrates. Little information is available in the literature regarding the digestion of carbohydrates and the absorption of glucose in the small and large intestine of the mature ruminant animal.

In advanced pregnancy and during lactation an animal is in a critical glucose balance resulting from lactose synthesis (Armstrong, 1965). Since the major precursor of lactose is blood glucose (Reiss and Barry, 1953) supplied primarily through gluconeogenesis of noncarbohydrate sources (Armstrong, 1965), the importance of any glucose absorbed from the gastrointestinal tract which would contribute directly to the maintenance of the blood glucose level is obvious.

Although it is estimated that only about 10 percent of the glucose requirement of the ruminant animal is absorbed from the alimentary tract (Armstrong, 1965), it is of interest to know the efficiency of glucose absorption and utilization of other carbohydrates in the small and large intestine of the mature ruminant.

The objectives of these studies were to determine; (l) the levels of the carbohydrases, maltase, lactase, sucrase, amylase, and cellobiase in the mucosa of the duodenum, jejunum, and ileum; (2) the rate of absorption of glucose in vivo in the duodenum, jejunum, ileum, cecum, and colon; and (3) the degree of utilization of maltose, starch, and cellulose in the duodenum, jejunum, ileum, cecum, and colon in mature sheep.