The Lys/Met and MP Calculator

Addressing AA Requirements

In chapter 5 of the NRC 2001 publication titled Protein and Amino Acids, the closing paragraph of the Requirements for Lysine and Methionine in Metabolizable Protein section makes the following statement..

"... implementation of diet formulation strategies that increase Lys and Met in MP to concentrations that approach or meet the requirement levels can result in more actual milk than MP Allowable milk. Indeed, achieving the optimum concentrations of the most limiting AA in MP is the first step in balancing diets for AA. The subcommittee encourages more research aimed at determining the ideal profile of EAA in MP of growing cattle and lactating cows. The results of such efforts are needed to combine protein supplements and ruminally protected AA in ways to meet AA requirements of dairy cattle with minimal MP, and thus, Minimal RUP."

In the paper titled "Amino Acid Balancing in the Context of MP and RUP Requirements", presented at the 2004 Florida Nutrition Conference, Dr. Chuck Schwab, University of New Hampshire, stated the following.

"The purpose of this paper is to emphasize the importance of providing the lactating cow with the correct balance of AA in MP, to explain why some AA are more limiting than others, to review how one balances for Lys and Met in the context of balancing for MP and RUP and some production responses that have occurred when the practice is implemented, and to share some preliminary data aimed at extending the application of NRC (2001) to predict lactation responses from changes in supply of MP-Lys and MP-Met."

Dr. Schwab served on the NRC 2001 subcommittee and was responsible for development of the amino acid sub-model. He has continued working to extend the application of the NRC model to accommodate the prediction of MP-Lys and MP-Met formulation targets for specified levels of milk and milk component production. The information presented at the Florida conference represents a very powerful tool for the formulation of lactating diets and as such we felt it should be incorporated into Formulate2's toolset. Since the work is preliminary and ongoing, the equations are implemented in the Calculator shown below as editable text easily facilitating revision as new data becomes available.

Lys/Met MP Equations Tab

Please note that the parentheses present in the equation scripts are necessary for the equation script solution engine to execute operations in the correct order. Also, the syntax of the script solution engine does not allow spaces in equation scripts and the variable names cannot be changed.

When the Calculator is accessed, if milk production and true protein values are present on the Animal & Production Inputs tab of the ration record, they are automatically imported to the Milk Target and Milk TP% fields of the Calculator. If the selected protein type is "Crude", the protein value will not be imported.

You may also manually enter or edit these values. The Calculator retains it's values even when Formulate2 is closed and the computer is turned off and will always display the data it most recently contained when accessed.

To solve the equations for the entered milk and milk true protein values, simply click on the Calculator Solve button. The resulting Met and Lys values will be placed MP Met and MP Lys gm reqd. fields. You may select the values you wish to use simply by clicking on the appropriate "Use this value" check box.

The last two steps needed to generate the export target values for Met, Lys and MP are to select the AA value from which the MP value will be calculated and then enter the desired concentration of the AA in MP.

Clicking the Refresh button will re-import the milk and milk true protein values from the currently displayed ration record. Clicking on the Clear button will remove all values and selections from the Calculator. Clicking on the Equations button will display the prediction equations panel as shown in the image below.

The Save and Restore buttons on the equation panel allow you to either restore the edited equations to their original state or to save the edited equations as the new default.

Clicking on the Export button places the export target values in the currently displayed ration record for immediate optimization.

Microbial CP Yield Tab

The inputs on this tab of the Calculator allow you to manually adjust the NRC model predicted microbial crude protein yield by a percentage of the model predicted value. Adjustments may be applied during the diet solution process or post optimization after a solution has been reached.

Applying the adjustment during optimization will have the affect of adjusting MP and AA required from digestible RUP. If your adjustment increases the predicted microbial yield, less MP and MP-AA will be needed from the diet and Formulate2 will solve the diet accordingly. Conversely, if the adjustment reduces the model predicted microbial CP yield, more MP and MP-AA will be required from the diet.

Adjustments applied post optimization will not affect the solution process but will show how the adjustment will affect MP supply and AA flow to the duodenum. These changes can be observed by reviewing the Ration Duodenal EAA Supply Summary and the Ration NE(l) and MP for Milk Production reports.

If either adjustment option is checked, the Ration record status bar will indicate that a modification to the NRC model predicted MCP yield is being made with the notation "MCP Mod: ON" as shown in the status bar image below.

Adjustments that you make are not retained in the ration record itself, however you may record the adjustment by including a notation in the Pen/Group description such as "Fresh and Early Lactation Animals MCP=103%". However, after restarting Formulate2 you must manually re-enter the adjustment indicated in your notation when either reformulating or viewing the last solution.

While the Calculator will retain adjustment values and adjustment option selections between program starts, adjustments are not automatically implemented when Formulate2 is started. When the program is first started, the status bar caption will read "MCP Mod: OFF". As long as the caption reads "OFF" no adjustments are being implemented.

However, the first time you access the Calculator your adjustment selections will be activated and the status bar caption will indicate "ON". To deactivate adjustments, simply uncheck both adjustment option check boxes.

Accessing the Calculator

The Calculator is easily accessed from your normal workflow activity via the Formulate pop menu as shown below and may also be selected from the Menu bar Formulate menu.

The values you see in the image above on the Nutrient Constraints grid for Lys, Met and MP were placed there simply by clicking on the Calculator Export button. You may also transfer values from the Calculator to the ration record by highlighting the value, clicking on the right mouse button and selecting Copy from the pop up menu. You may then paste the value into the ration record.