Feeding the high producing dairy cow has been an increasing challenge as consumers desire animal products with less fat and higher protein. Producers, on the other hand, desire feeding programs and new feeding strategies that not only improve production, but also herd health. At ANC, we are expanding ration formulation programs to help ensure that the intake of usable nutrients by the cow are not only in balance, but also minimize nutrient loss in animal waste. The results of these efforts have been increased dry matter intake and improved feed efficiency, which results in more profit for the dairy producer.

There are many nutritional aspects to consider when feeding the high producing cow, such as energy, fiber, minerals and vitamins. This article will focus on types of protein such as rumen undegradable intake protein (RUIP), amino acids (AA's), and rumen microbial protein. RUIP is also referred to as rumen undegradable protein (RUP), bypass protein, or undegradable intake protein (UIP). This is the portion of feed protein that escapes ruminal degradation and passes to the small intestine. We know that sources of RUIP differ greatly in nutritive value. Therefore, proper selection and balancing of protein sources is required for maximizing milk production and milk components. Ruminally protected amino acids are now available and can be added to the ration as separate ingredients if necessary. We have used some of these at ANC. However, the cost of these AA's are generally higher than AA's in their natural form from feedstuff sources.

Like poultry and swine, high producing dairy cows have metabolic requirements for specific amino acids, rather than just a crude protein requirement. Amino acids have always been available to the cow by ruminally synthesized protein and RUIP sources, even though the mode of their utilization was not known. These AA's must be digested in the small intestine to be released and absorbed. Protein digestion starts in the abomasum with acid-pepsin digestion and is completed in the small intestine with pancreatic and intestinal enzymes referred to as proteases. Absorbed AA's are the building blocks for the synthesis of body and milk proteins. Of the twenty found in plant and animal protein, ten are considered to be "essential". Essential amino acids (EAA) are those that the cow must absorb from the small intestine, because the body cannot synthesize them in adequate amounts to meet metabolic needs. The cow has specific requirements for each of these AA's. When they are absorbed in the correct balance, the total efficiency of protein usage is greater. Conversely, when EAA's available for absorption are not in the same balance as required by the cow, efficiency of use decreases. The EAA in shortest supply relative to requirements is called the first limiting AA. The other 10 AA's are called "nonessential", because the animal does not have to absorb each of them in specific amounts.

The best source of AA's are ruminally synthesized microbial protein. Protein balance in general is quite dependent on the rest of the ration! Diets must optimize rumen function, making it a priority to balance for proper fiber and non-fiber carbohydrate (NFC) levels, along with minerals and micronutrients. It puzzles me that many consultants and feed companies emphasize the purchased protein fraction of the ration, with lesser concern for proper fiber nutrition. I guess this is because they make their living through the sale of protein blends or protein ingredients.

Microbial protein is the major source of protein available to the cow, supplying 50% or more of the amino acids when rations are properly balanced. This is provided mainly by a mixture of bacteria and protozoa, which works in the rumen to break down feedstuffs. These multiply and pass along with the rest of the ruminal ingesta to the lower gastrointestinal tract. The amount of microbial protein that is produced is dependent on sources and amounts of ruminally degradable carbohydrates and proteins, along with total feed intake, ruminal pH, and other factors.

The second major source of absorbable AA's is RUIP. This is the protein fraction that is fed to the cow through protein supplements, grains, and forages. All feedstuffs contain some RUIP. However, forages and most energy feeds contain low amounts of bypass protein on a per pound basis. The RUIP fraction of oilseed meals (soybean, linseed, canola, cottonseed, and sunflower) is relatively low compared to by-product feeds such as corn distiller's grains, brewer's grains, corn gluten meal, and animal proteins (meat and bone meal, fish meal, and blood meal).

The amount of RUIP in oilseeds and meals can be increased substantially by heat treatment. Many high quality products produced by these methods are available. Some examples include roasted beans, extruded beans, and commercial sources of heat treated expeller soybean meal such as Soy-Plus. The heat treating process, when properly done, increases the amount of RUIP, especially the AA, lysine, which is used in the greatest quantity by ruminants. Products that are heat treated under conditions that provide greatest quality control are of higher value when accurately balancing a ration. Please check with your ANC consultant as to which sources are the most economical in your situation! n Return To Table Of Contents