ANSC 438 Home / Beginning / Milk Composition / Mammary Structure
Mammary Development / Mother & Neonate / Lactation / Mastitis

Milk Composition & Synthesis
Resource Library


Milk Synthesis
Lactose


SOURCES OF GLUCOSE IN RUMINANTS

The importance of glucose for milk synthesis means that the supply of glucose to the mammary gland is critical for milk production. Where does this glucose come from? In the ruminant, very little dietary glucose makes it past the rumen to be absorbed in the intestine. While some glucose may be stored in the liver as glycogen, which acts as a readily releasable pool of glucose, very little glycogen is left in the liver after the first few days of lactation. About 45 to 60% of blood glucose in ruminants is synthesized from propionate in the liver by a process called gluconeogenesis. While gluconeogenesis occurs in all mammals, ruminants are particularly dependent upon gluconeogenesis for generation of glucose. Even so, blood glucose levels in ruminants are only about 1/2 those found in monogastrics. As indicated in the image below, proprionate, a major volital fatty acid generated from rumen fermentation of carbohydrates, is a major precursor for gluconeogenic production of glucose. The other source of precursor carbons for synthesis of glucose via gluconeogenesis comes from metabolism of several of the amino acids. These are known as glucogenic amino acids and include most amino acids except for leucine. Note that gluconeogenesis, that is production of glucose from precursor metabolites, occurs in the liver and to a uch more limited degree in the kidney cortex, but is not thought to occur in the mammary tissue.

Gluconeogenesis


Lactose
Milk Composition & Synthesis
Resources