Lactose is a disaccharide and as such it has to be broken down by the enzyme lactase to its constituent glucose and galactose before absorption in the small intestine and utilization by the body can occur. Newborn mammals are well endowed with lactase but production of the enzyme falls off rapidly after weaning, so that adult animals are able to digest only small amounts of lactose. Lactose, the major carbohydrate of milk, controls milk volume by maintaining its osmolarity. Therefore, the rate of lactose synthesis in the epithelial cells of the mammary gland serves as a major factor influencing milk volume. Glucose is the main precursor of lactose synthesis in mammary gland epithelial cells. However, a lactating mammary gland cannot synthesize glucose from other precursors due to the absence of glucose-6- phosphatase and so is dependent on the blood supply for its glucose requirement. However, objective of this review discussing importance lactose and its effect on fertility, feed intake, ketone bodies, nutrient digestibility.
