Arithmetic and Minerals

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Arithmetic and Minerals

Livestock Update, January 1997

Mark L. Wahlberg, Animal and Poultry Sciences

Recently I received a request from an Extension Agent for some assistance with a mineral formulation problem. The problem and method of solution are detailed below.

Situation: A producer is using a commercial mineral product that contains Selenium at 0.0052%. The producer wanted to increase the Selenium level in the mineral using a Selenium premix that contains .06% Selenium. How much of the Selenium premix needs to be added to the commercial mineral to have the final mixture contain 80 Parts per Million?

Background Information: There are a few basic facts needed to solve this problem. They are:

To convert Percent to Parts per million you move the decimal point 4 spots to the right.
Consequently, the Commercial mineral has 52 Parts per Million (PPM) and the premix contains 600 PPM of Selenium (Se).
One Part per Million is equal to One Milligram per Kilogram
There are 2.205 Pounds in a Kilogram.
The Commercial Mineral comes in a 50-Pound Bag.

The Solution: First of all we need to calculate how many milligrams of Se are needed in 50 pounds of commercial mineral plus Se-600 in order to have the total mixture contain 80 PPM.

80 PPM = 80 mg per Kg of Mineral

50 Pounds / 2.205 Pounds per Kg = 22.7 Kg

Se in the 50-pound bag = 22.7 Kg X 52 Mg/Kg = 1180 Mg of Se

Mg of Se needed in 50-pounds to provide 80 PPM = 22.7 Kg X 80 Mg/Kg = 1816 Mg

Now, calculate the amount of Se to be added by the 600 PPM premix, and the amount of premix needed.

Extra Se needed is 1816 - 1180 = 636 mg additional Se

There are 600 PPM or 600 Mg in 1 Kg of the high Se premix.

636 mg needed/600 mg in 1 kg = 1.06 Kg of high Se premix.

1.06 Kg X 2.205 Pounds in 1 Kg = 2.34 Pounds of high Se premix.

Finally, calculate the concentration (PPM) of Se in the final mixture.

Final Se content of the mixture is 1180 mg in 22.7 Kg + 636 Mg in 1.06 Kg = 1816 mg in 23.76 Kg

1816 mg / 23.76 Kg = 76.4 Mg/Kg or 76.4 PPM.

You will note that the concentration is 76.4 PPM and not 80 because we added 2.34 pounds more material to the 50 pounds of mineral. However, it is certainly close enough to the desired outcome to be considered the proper amount, especially considering that we cannot estimate cow intake of mineral very accurately.

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