The milk volume is contingent upon glucose and galactose (which is ultimately synthesized fro glucose) in the production of milk because it is from glucose that one may synthesize lactose. Lactose is a glucose-galactose disaccharide. Galactose is synthesized from glucose and taken up by the mammary gland i.e. both hexose units of lactose are ultimately derived from glucose. Lactose is the agent responsible for the milk volume as it is a very potent osmotic solute. Lactose synthesis accounts for >80% of mammary glucose uptake which acts to fuel galactose synthesis. It is for these reasons that milk yield is directly related to the RATE of mammary lactose synthesis, while milk lactose concentration (%) stays relatively constant within and between animals. Milk fat is > 98% triacylglycerols and contains a wide range of fatty acids. The two main sources of fatty acids are from: De Novo Synthesis from acetate and 3-hydroxybutyrate. And, uptake of preformed long-chain fatty acids from plasma lipoproteins (esp. chylomicrons).
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