Factors affecting the composition of cow's milk

Abstract

SummaryFat is by far the biggest contributor to the variations in total solids content of milk caused by dietary change. There is a progressive fall in milk fat concentration as the ratio of concentrates to fibrous feed is increased. The overall effects of diet on milk fat yield may be quite small since decreases in fat content tend to be counter balanced by increases in total milk yield. Manipulating the protein content of the diet in a range appropriate to practical feeding systems does not significantly affect milk fat content, although change can be achieved under experimental conditions. Including fat supplements in the diet of dairy cattle can affect both the amount and composition of fatty acids in milk. Any strategy that leads to a reduction in the ratio of lipogenic to gluconeogenic volatile fatty acids in the rumen is likely to result in a significant reduction in milk fat content.While it is feasible to modify fat content and composition over a wide range, protein concentration varies less than 10 per cent in response to dietary change.Lactose, the major osmotically active component of milk, plays a vital role in determining the volume of milk secreted. It follows that the concentration of lactose in milk is relatively constant and unaffected by diet, although severe underfeeding may result in a low lactose concentration.