Moderate levels of fat are good and will usually support increased production of milk and milk fat. However, excess fat may negatively impact production and the synthesis of milk components. Rumen microbes do not use fat as an energy source and cannot digest it. Thus, feeding excess fat can decrease the production of microbial protein. If feeding fat, it is best to feed a variety of fat sources, including those that are available in the rumen and those that are inert in the rumen.
Rumen inert fat sources include calcium salts of fatty acids and hydrogenated fats.
Dietary protein Diets that stimulate microbial growth will also promote milk protein production. Milk protein is affected by the amount and composition of the dietary protein. In fact, in recent years, dairy nutritionists have begun focusing on amino acids, the building blocks of protein. The swine and poultry industries have been balancing diets for crude protein and specific amino acids for a number of years. Recent advances in ruminant nutrition research are allowing dairy nutritionists to begin evaluating the amino acid profile of the lactating cow diet.