B86 Pearson Square Balancing a Ration

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Lesson Outline

Calculating amounts of feed needed

Selecting feed ingredients

Using the Pearson square

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Pearson Square

The Pearson square is a tool used for simplifying and balancing rations.

It shows the proportions or percentages of two feeds to be mixed together to give a percentage of the needed nutrient.

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Calculating Feed Amounts

If pigs have an industry average feed conversion ratio of 3.5, and you purchase a 50 lb weaner pig and want him to weight 250 pounds by the fair, how many pounds of feed is it going to take to raise this pig to 250 pounds?

250 pound finished hog minus 50 pound weaner = 200 pounds of gain.

200 pounds X 3.5 = 700 lbs of feed. A feeding standards table shows that an 18% crude protein ration

is needed.

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Select the Feed Ingredients

Feeds should be selected based on the price of the feed, the availability of the feed, and the desirable nutrients found in the feed.

Lets say corn and soybean meal (SBM) are selected as feeds. A feed composition table indicates:

Corn has 8.9% crude protein SBM has 44.4 % crude protein

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Using the Pearson Square

Use the Pearson square to calculate how much corn and soybean meal need to be mixed together to make 700lbs. of feed and still achieve 18% crude protein.

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Step 1

Draw a 1 to 2 inch square. Place diagonal lines across the square.

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Step 2

Write the percentage of crude protein needed by the animal in the center of the square where the diagonal lines cross.

(You would have to look that information up on a feed chart for that animal.)

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Step 3

Write the feeds to be used at each corner.

The primary feed always goes in the bottom left.

The supplementary feed in the top left. (In this case it doesn’t matter. If you were feeding hay and corn, hay would be the primary feed.)

Place the percent of crude protein in the feeds after the name of the feed.

• Corn• 8.9%

• SBM• 44.4%

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Step 4

Take the protein level of each feed ingredient and subtract it from the amount of protein needed in the center of the box and record it in the opposite corner.

44.4 – 18= 26.4 18 – 8.9 = 9.1

• Corn 8.9% 26.4 parts corn

• SBM 9.1 parts • 44.4%

SBM

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Pearson Square

Note: A negative number is undesirable, so if the protein in the feed is higher than what is needed, just subtract what is needed from the feed. However, if the protein in the feed is a smaller number than what is needed, subtract what is needed from what is in the feed.

44.4 – 18= 26.4 18 – 8.9 = 9.1

• Corn 8.9% 26.4 parts corn

• SBM 9.1 parts • 44.4% SBM

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Step 5

The numbers at the two right corners are parts of the two feed ingredients that are needed.

26.4 parts corn +9.1 parts soybean meal (SBM) 35.5 total parts

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Pearson Square

Corn 26.4 parts corn 8.9% 35.5 total parts

SBM 9.1 parts SBM44.4% 35.5 total parts

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Step 6

The percentage of each feed needed in the ration can be found by dividing the number of parts by the total parts, then multiply by 100.

26.4/ 35.5 = .744 x 100 = 74.4% corn 9.1/ 35.5 = .256 x 100 = 25.6% sbm

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Pearson Square

Corn 26.4 parts corn 8.9% 35.5 total parts 74.4%

SBM 9.1 parts SBM44.4% 35.5 total parts

25.6%

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Step 7

The amount of each feed ingredient for a large batch of feed is determined by multiplying the percentage of each by the total amount of feed desired.

Our batch of feed = 700lbs 700lbs x .744 = 520.8lbs Corn 700lbs x .256 = 179.2lbs SBM

700lbs 0f feed @ 18.% Crude Protein