ISSUE FOCUS FEED & ADDITIVE MAGAZINE March 2026 55 2. Review Crude Protein and protein fractions a. Crude protein should be a minimum of 8% if feeding forage only. Higher protein is better if you are feeding pregnant, lactating, or growing animals b. Soluble protein should be a minimum of 25% and preferably 30-35% c. Rumen degradable protein – Look for higher values (>65%) 3. Evaluate Fiber Carbohydrates a. Calculate the ADF to NDF ratio. Values close to 0.6 or lower indicate a grass forage. Values close to 0.8 or above indicate a legume forage. Values in between indicate mixed forages b. Grass forages with NDF > 65% should not be fed to higher-producing animals but could be used in maintenance and high body condition score animals c. Legume forages with NDF > 50% are very mature and will decrease potential feed intake d. If Lignin value is provided, calculate the lignin to NDF ratio as a percentage. With grasses, values < 8.5% will be more readily digested. With legumes, values < 17% will be more readily digested. Higher values within each forage type indicate a more lignified cell wall and more slowly fermented forage 4. Evaluate Degradable Carbohydrates a. Review the NFC and NSC values for the forage or feed b. With grass forage, a good NFC value would be 20-25%, whereas with legume forages the NFC will be much higher (35-45%), but this is mostly due to fermentable fiber from pectin substances c. Starch content of forages is typically less than 3%. 5. Review Macrominerals a. Calculate the calcium to phosphorus ratio. It should be 2:1 or slightly higher. Legume forages will be very high (> 6:1). b. Check calcium content in grass forages and be sure it is above 0.45%. Higher values will be needed for lactating and growing animals. c. If the phosphorus content is greater than the calcium content – DO NOT use! This will greatly increase potential for urinary calculi in males. d. Forages with phosphorus content > 0.25% typically are over-fertilized. See if the potassium value is also increased. e. Forage magnesium < 0.10% is low and typical of some grasses. Legumes typically have higher magnesium, at 0.2% or more f. Forage potassium is always higher than required. In most cases, this is not a problem. Potassium values >2.5% are very problematic. 6. Evaluate trace mineral values a. Typical iron content is between 100 and 300 ppm. Values over 1,000 ppm usually indicate soil contamination of the sample. b. Manganese is much higher in grass than legume forages. A value around 40 ppm in forage is desired. c. Zinc is typically low in all forages (<30 ppm). d. Copper is variable depending upon geography. Forage copper is higher east of the Mississippi River (> 9 ppm). Hay harvested from dairy farms may have higher copper (>15 ppm) due to their use of copper sulfate footbaths. Potential toxicosis could occur with forage with > 20 ppm copper e. Molybdenum concentration should be determined in all feeds due to its impact on copper status. High forage molybdenum is sporadic in many geographic regions. A copper to molybdenum ratio < 4:1 will risk possible copper deficiency issues. A high ratio (>16:1) places the animals at risk for copper toxicosis. With this systematic approach to understanding the forage or feed analysis report, one can readily make informed decisions on the appropriateness of a forage for their feeding program or identify potential nutritional risks underlying an animal disease issue. About Robert Van Saun A professor of veterinary science and extension veterinarian with Pennsylvania State University, Dr. Robert Van Saun provides extension programs across species on various nutrition, animal health, and reproductive topics regionally, nationally, and internationally. His research interests include the role of nutrition in animal health and performance, especially pregnancy nutrition, and improving diagnostic tests to evaluate nutritional status.
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