Balancing amino acids becomes a best practice

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A notable addition to the best practices of leading dairy nutritionists is the balancing of amino acid levels to promote higher milk yield and components.

“There truly is a pot of gold waiting for those individuals who master the balancing of amino acid levels,” says Dan Luchini, Ph.D., Manager – Ruminant Products Technical Services, Adisseo. The ability to design and manage the amino acid levels in rations continues to evolve. Many of today’s formulation programs were designed prior to current amino acid balancing concepts.

The three basic ration formulation models used in the United States -- NRC 2001, CNCPS and CPM -- have evolved with improved equations to better predict a cow’s responses to amino acid balancing. In addition, the different amino acid fractions in crude protein (CP) are now recognized, and each is given a specific degradation rate.

Big picture, the cow’s nutritional requirements call for grams of amino acids in metabolizable protein (MP), not for crude protein. Therefore, rations are being balanced to optimize the concentrations of the first two limiting amino acids. These are metabolizable lysine and metabolizable methionine in MP. Balanced rations contain a near-ideal lysine to methionine ratio.

The optimal concentrations for lysine and methionine in MP for the NRC, CPM and CNCPS models were determined by Whitehouse et al (2009) by applying the indirect dose-response approach. Yet the optimal lysine and methionine concentrations differ by model. Levels are much higher for CPM versus NRC 2001 and CNCPS due to its higher microbial contribution predictions.

In practice, achieving 97 percent of the optimal concentrations of LYS and MET may be a realistic goal due to ingredient availability.

Practical Target Formulation Levels for Lysine and Methionine by Ration Formulation Model

 

Milk Protein %

Milk Protein Yield

Practical Formulation Guidelines

Target Formulation Levels*

LYS:MET Ratio

Target Formulation Levels*

LYS:MET Ratio

LYS & MET as % of MP

LYS:MET Ratio

NRC

Lys

6.60

2.97

6.89

2.82 

6.74

2.89  

Met

2.22

2.44

2.33

CPM V.3

Lys

7.24

2.90

7.28

3.00

7.26

2.95

Met

2.49

2.43

2.46

CNCPS v.6

Lys

6.48

2.78

6.54

2.92

6.51

2.85

Met

2.33

2.24

2.28

When lysine and methionine are provided in optimal balance, the efficiency of nitrogen utilization improves which promotes higher milk yields and component levels. By concentrating the levels of lysine and methionine in MP, total MP and crude protein can be reduced which is good for the environment and cows.



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