ISSUE FOCUS 40 FEED & ADDITIVE MAGAZINE March 2023 3. Subtract the nutrient value from the nutrient requirement on the diagonal. a. 10.8 – 11.0 = 0.2 parts chopped hay b. 12.25 – 11.0 = 1.25 parts corn silage 4. Add the parts of each ingredient and divide by the total to calculate the percent of the ration that each ingredient will represent. a. 0.2 + 1.25 = 1.45 total parts b. Chopped Hay: (0.2 ÷ 1.45) × 100 = 13.8% c. Corn Silage: (1.25 ÷ 1.45) × 100 = 86.2% 5. Mixing a 1,000 lb batch on a dry matter basis a. Chopped hay: 1,000 lb × (13.8 ÷ 100) = 138 lb b. Corn Silage: 1,000 lb × (86.2 ÷ 100) = 862 lb The Pearson Square works the best for rations using only two ingredients. When using the Pearson Square, nutrient concentrations of the feeds used and the requirement need to be on the same basis, as-fed or dry matter. Most feed analysis is provided on a dry matter basis. Therefore, once the formulation is complete, the numbers should be converted back to as-fed for easy use when feeding. It is always important to check your math after completing a Pearson Square. To check the math using the Figure 1 example: • 138 lb chopped hay × 12.25% CP = 16.9 lb CP • 862 lb corn silage × 10.8% CP = 93.1 lb CP • Cow’s requirement = 1,000 lb × 11% CP = 110 lb CP • Check: 16.9 lb CP + 93.1 lb CP = 110 lb CP Since using the dry matter basis for our formulations, we need to convert to as-fed for ease of use when mixing the diet. The chopped hay has a dry matter of 88% and the corn silage has a dry matter of 35%. To convert dry matter to as-fed, we will take the weights of the 1,000 lb batch and divide by the dry matter percent. • Chopped hay: 138 lb ÷ (88 ÷ 100) = 157 lb as-fed • Corn silage: 862 lb ÷ (35 ÷ 100) = 2,463 lb as-fed USING A PEARSON SQUARE WITH MORE THAN TWO INGREDIENTS Although a Pearson Square is easiest and only includes options for two ingredients, formulations can be made with more. Figure 2 is an example of using more than two ingredients. In this example, a final diet formulation of 15% CP is needed. In this example, there is a supplement containing 50% soybean meal (SBM) and 50% corn gluten feed (CGF) and a grain mixture containing 60% corn grain and 40% soybean hulls (SBH). Supplement mixture • 50% Soybean meal with 54% CP • 50% Corn gluten feed with 24% CP Grain mixture • 60% Corn grain with 10% CP • 40% Soybean hulls with 12% CP Figure 2. Pearson Square model using more than two ingredients. 4.2 parts Supplement Supplement Grain Grain 24 parts 28.2 total parts 39.0% 10.8% 15%
RkJQdWJsaXNoZXIy MTUxNjkxNQ==