Milk91 for Combining Forage Yield and Quality into a Single Term

Terry Howard, Randy Shaver, and Dan Undersander

Milk91 is an easy to use Excel 3.0 spreadsheet that uses the forage analysis (crude protein, acid detergent fiber, and neutral detergent fiber) to calculate an approximation of a balanced ration using NRC values. It differs from Milk95 in that ADF rather than digestibility is used to calculate energy. The spreadsheet maximizes forage in the dairy ration and calculates the milk from forage based on the percent of energy in the ration coming from the forage.

Background Information and Recommendations Concerning Use Of Milk91

Previous Milk/Acre and $ Return/Acre equations were largely ranking procedures for combining yield and quality of forage. Other animal and management factors were not considered. This new spreadsheet gives figures that are more biologically sound. Figures result in correct ranking of forages but should not be considered as predictive of milk response in specific situations for the following reasons:

1. the calculations are simplified to reduce inputs for ease of use
2. farm to farm differences exist.
3. the spreadsheet does not consider genetic or environmental differences affecting feed efficiency.

Differentials from comparisons of forages approximate realisitic values.

Remember the following cautions when using this spreadsheet:

1. Do not use different values for yield or quality measurements that are not significantly different statistically. Animal response calculations are more sensitive than our measurement techniques. The spreadsheet will show a Milk/Ton and $ Return/Acre difference when yield and quality were not statistically different.
2. The equations approximate a balanced ration for energy, crude protein, fiber and UIP.
3. The spreadsheet calculates the percentage of total dietary energy from forage, subtracts a maintenance requirement of the cow from the forage energy and then calculates milk/ton of forage.
4. Return/Acre is calculated by milk production times price minus the $3 per head per day animal overhead charge; this figure multiplied by the percentage of total ration TDN that came from forage and then production costs are subtracted calculation.
5. We recommend that $ Return/Acre, not Milk/Acre, be used to make comparisons.
6. Inputs such as cow weight, milk price, etc can be changed but we recommend that, for general educational purposes, they be left as are for yearly periods or longer so that different individuals do not get different results from the same forage and confuse the public.

Use of MILK91

Standard inputs that are needed are forage yield, sample dry matter (most results are reported on dry matter basis and sample DM should be 100), forage crude protein, ADF, and NDF.

• Economic inputs may be left at the defaults or changed as needed.

For modeling purposes you may change parameters such as cow weight, milk price, lb milk/day, % milk fat, stage of lactation, feeding losses, corn cost, soybean meal cost and overhead charge. We recommend that you do not change these parameters when using for educational purposes to avoid confusion to the public.

The spread sheet currently contains common forages and their average quality. You can enter data into columns A through L. Depending on you spreadsheet settings, it may be necessary to push F9 after entering data for calculation of results. Calculated results are in columns M through Q. Columns to the right of Q are used for calculations. A second table (table 2) below the first may be printed if desired to give more information on the figures involved in milk/acre and $ return/acre calculations. It may be useful to look at Adjusted milk per day to see if given forage can support an inputed milk level.

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