The ability to change milk composition via cow diet can lead to increases in the yield and functional properties of dairy products. Inducing such changes via diet can lead to more rapid and reversible changes to milk composition than other contributing factors . However, some components are more readily changed than others. Milk fat, for example, is readily altered by changing the forage:concentrate ratio or by feeding oilseeds containing high levels of polyunsaturated fatty acids. Such changes can improve the yields, functional properties and perceived healthiness of butter and other products. Similarly, the mineral composition can be altered by supplementation, which has implications for product functionality and human health. Unfortunately alterations of the amount and type of milk protein are difficult to achieve via dietary manipulation. Maintaining an adequate supply of metabolisable energy to ensure maximum protein concentrations is probably the only reliable strategy in this regard.