ABSTRACT
The Food Agricultural Organization estimates that 6 billion of the 7 billion people in the world consume milk and milk products, and 150 million households around the globe are engaged in milk production. Losses of nitrogen, phosphorus and greenhouse gases to the environment from livestock production units can create environmental degradation. Nutritional strategies to improve nitrogen efficiency and milk protein synthesis in dairy cows largely from urea excretion. Mechanical influences include milking and suckling stimuli, but also mechanical adhesion of epithelial cells in the gland which enhances cell differentiation. If energy is limiting, particularly glucose availability, milk protein synthesis is reduced, as is milk volume. Lactose is synthesised in the Golgi apparatus in mammary cells along with milk proteins. Because rumen fermentation significantly alters feed inputs, the prediction of supply of amino acids (AA) to the duodenum is not straightforward. A problem with AA supplementation in dairy cows is rumen microbes, which readily degrade AAs.
