Balancing for amino acids has become a new standard in dairy nutrition. Gone are the days when we created lactating rations with protein ingredients based on crude protein. Today, we know that balancing for metabolizable protein is a more precise, economical and beneficial way to maximize dairy ration effectiveness.

Crude protein has lost favor in dairy nutrition for a number of reasons. For one, cows don’t require crude protein. They do require specific amino acids they can metabolize to make milk, fat and protein. Much of the rest of the protein fractions delivered via crude protein are simply wasted resources. They are excreted via manure and urine, resulting in unnecessary emissions of nitrogen.

Today’s dairies also must operate in a climate of high-cost protein sources that vary widely in quality and consistent availability. So it makes sense to fine-tune the protein components of rations to maximize their economic value to the dairy business and their benefit to the cow and the environment at the same time.

Zeroing in on amino acids
Supplementation with accurate amounts of specific amino acid products can allow for more targeted delivery of desired protein fractions compared to relying on feedstuffs alone. Currently, the two amino acids that are commercially available via supplements are methionine and lysine.

Balancing for these amino acids has been shown to improve ration protein cost efficiency while at the same time increasing production of milk or components.

Research on the effects of amino acid balancing on milk and component production has shown that milk volume is driven by lysine whereas components are increased by balancing for both lysine and methionine. So if you are paid solely on milk volume, balancing for lysine is most beneficial. If you are paid for volume and receive premiums for components, you’ll want to balance for both.

Both methionine and lysine are considered the most “limiting” amino acids for milk production, meaning the production response of the entire ration depends on providing adequate levels.

If one or both is deficient in the ration, milk/component production will only be based on the lowest-level amino acid. Other nutrients that exceed the performance capability of the most limiting amino acid are wasted.

That’s why it’s important to deliver optimal levels of both amino acids while minimizing the overdelivery of other nutrients. Your nutritionist has access to nutrition models and computer software that can help with these calculations. Another important consideration is selection of the source you use to achieve desired levels.

Lysine selection can be tricky
There are a number of options available for delivering lysine into the dairy ration. They fall into two categories: feedstuffs and supplements. Cows depend on consistent, high-quality protein sources to achieve and maintain high production levels.

Blood meal contains high levels of metabolizable lysine and probably is the most popular choice of commodity feedstuffs used to deliver lysine. But blood meal presents two significant challenges: It is fairly expensive and has been shown to be highly inconsistent in the levels of lysine it supplies.

One study at the University of Minnesota compared the percentage of lysine digestibility in four samples of blood meal. They ranged widely, from 80 percent to just 53 percent. That level of inconsistency from one load to the next makes it challenging to maintain consistent amino acid levels in the daily ration.

This does not mean all blood meal is bad, just that there is poorly digestible blood on the market and you need to make sure your supplier is sourcing blood meal that is digestible.

Several commercial supplements also may be used to supply specific levels of lysine. Most of these are rumen-protected (bypass) products intended to travel through the rumen intact and then pass to the small intestine, where they are digested, absorbed and utilized by the cow. Rumen protection is important because if the product loses its stability in the rumen or before, its value is destroyed.

Unfortunately, some products have been found to be protected so well that they pass through the entire digestive system and exit through the feces intact. They are of no value to the cow because their overprotection prevents digestion or absorption anywhere in the digestive tract.

Levels of metabolizable lysine also vary on an availability-per-gram basis among products. While no commercially available products have 100 percent availability, choosing a product that has the highest percentage of metabolizable lysine on a per-gram basis is an important economic consideration. PD

For more information, contact Dr. Dave LaCount by email or call (920) 716-1700.

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Dave LaCount
Dairy Nutritionist
Purina Animal Nutrition