Balance Dairy Rations for Amino Acids

April 9, 2012 09:38 AM

Source: Adisseo

Existing knowledge of amino acid nutrition and models for dairy ration formulation are more than adequate for dairy nutritionists to take the first steps into amino acid balancing, according to Charles Schwab, Professor Emeritus of Animal Sciences, University of New Hampshire. This is particularly true if the nutritionist has not yet begun balancing rations for lysine and methionine or are not doing so correctly.
“The benefits are usually too large to justify not balancing amino acid levels, particularly if there is an interest in optimizing the efficiency of nitrogen utilization, dairy herd health and profitability,” Dr. Schwab says.
The responses achieved by balancing the levels of lysine and methionine in the diet’s metabolizable protein (MP) depend on one’s starting point, according to Dr. Schwab. “Where possible, field nutritionists with experience in balancing for lysine and methionine, also lower dietary rumen degradable protein (RDP) and/or rumen undegradable protein (RUP), if the previous diets allow,” he adds. 
This often reduces the added expense of replacing low lysine protein supplements with high lysine protein supplements and the cost of adding one or more rumen protected methionine sources to the diet. When employing these feeding strategies, field nutritionists typically report a return on investment (ROI) of 2.5 or higher when balancing for lysine and methionine in MP, according to Dr. Schwab.
In a 2007 international presentation, an average ROI of 3.35:1 was reported in a 10-herd Wisconsin study conducted the previous year. The ROI ranged from 1.1 to 5.5 for the 10 individual herds. Increases in butterfat content and milk yields are also common and contribute to a favorable ROI.
Balancing diets for lysine and methionine is a management tool for increasing dairy herd profitability. Increases in income over feed costs approaching 40-50 cents per cow per day have been reported by nutritionists as a result of both more precise balancing for RDP and RUP and balancing for lysine and methionine.
In addition, balancing rations for lysine and methionine enables the return of high milk component concentrations (3.2-3.4% protein and 4.0% fat) along with improved health and breeding in high-producing Holstein herds, according to Dr. Schwab.
“In retrospect,” he says, “such levels of performance should probably be expected when the limiting amino acids are no longer limiting and cows are finally able to realize their genetic potential. Increases in milk protein concentrations are usually the first responses observed when diets are balanced for lysine and methionine. Nutritionists with years of experience balancing for lysine and methionine, however, would suggest that changes in milk protein concentrations, while the initial and most visible responses, are only the tip of iceberg regarding the array of benefits realized when rations more adequately meet the cow’s dietary requirements for the most limiting amino acids.”
Sidebar: Feeding Strategies
To fully realize the production and performance benefits of balancing diets for amino acids, the following feeding strategy is recommended by Charles Schwab, Professor Emeritus of Animal Sciences, University of New Hampshire.
Feed a mixture of high-quality forages, processed grains, and byproduct feeds that provide a blend of fermentable carbohydrates and physically effective fiber that maximize feed intake, milk production, and yield of microbial protein. The concentrations of lysine and methionine in rumen microbes far exceed concentrations in most feeds.
Feed adequate but not excessive levels of rumen degradable protein (RDP) to meet rumen bacterial requirements for amino acids and ammonia. Realizing the benefits of feeding a balanced supply of fermentable carbohydrates on maximizing yields of microbial protein also requires balancing diets for RDP. Rumen degraded feed protein is second only to fermentable carbohydrates for the largest requirement by rumen microorganisms.  Rumen degraded feed protein supplies the microorganisms with peptides, amino acids, and ammonia that are needed for microbial protein synthesis.
Feed high-lysine protein supplements or a combination of high-lysine protein supplements and a rumen-protected lysine supplement to achieve concentrations of lysine in the metabolizable protein that come as close as possible to meeting the optimal concentration.
Feed a rumen-protected methionine supplement in amounts needed to achieve the optimal ratio of lysine and methionine in metabolizable protein.  Feeding a rumen-protected methionine supplement in conjunction with one or more of high-lysine protein supplements is almost always necessary to achieve the correct lysine-to-methionine ratio in metabolizable protein.
Do not overfeed rumen undegradable protein. Take advantage of the higher quality RUP that results when balancing for lysine and methionine!

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