ARM & HAMMER Animal Nutrition

All of the newer dynamic models for balancing rations for cows no longer use the older more ill-defined parameter of crude protein (CP). Rather, they try to balance for what the cow truly needs, which is metabolizable protein (MP). While CP is a catch-all measurement for all types of nitrogen in feeds, MP is the amount of true protein that arrives in the intestine of the cow. To illustrate the uselessness of CP, two diets with the same CP content can deliver vastly different amounts of MP to a cow. The MP provides the supply of amino acids to the cow for her true needs in biological functions, with our focus being on milk production. There are two sources of MP available for the cow. One is the true protein in the diet that escapes degradation in the rumen. This is called rumen undegradable protein, or RUP. The second source is the bacterial protein produced by the rumen microbes. The rumen microbes produce their protein as they multiply in the rumen while fermenting various carbohydrates (fibrous and non-fibrous) and use the rumen degradable protein (RDP) as a source of nitrogen. Rumen undegradable protein seems to receive the most attention by many nutritionists, but by far the bacterial or microbial protein is the most important and reliable source of MP for the dairy cow for two reasons. First, microbial protein can satisfy more than 50 % of the total MP needs for even the highest producing cows in well-formulated diets. Intuitively, the higher the amount of MP from microbial protein, the more efficient is the cow’s rumen at fermenting and digesting feeds. Secondly, the amino acid profile of the microbial protein is very consistent and is close to ideal in meeting the cow’s needs. Therefore, every time we can increase microbial protein production in the rumen, we are making the cow more efficient in her use of feeds and supplying a more ideal protein source to the cow