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University of Minnesota Extension

Evaluating amino acid levels in forages and horses

Quick facts

  • Cool-season grass and alfalfa are higher in amino acids than teff.
  • When grazed by horses, the only difference in blood amino acid levels was a decrease in threonine levels for horses grazing teff.
  • While alfalfa and cool-season grasses were higher in protein and lower in fiber, the horses grazing teff had similar blood amino acid response.
Horse grazing teff grass

Forage plays a key role in the horse’s diet. Horses usually eat cool-season grasses, legumes (e.g. alfalfa) or warm-season grasses (e.g. teff) as hay or pasture to meet their forage needs.

These forage types differ widely in their nutritional content. One main difference is their protein content. Legumes usually have the highest protein content (CP), while warm-season grasses usually have the lowest.

Protein affects growth, muscling and muscle repair in horses. While crude protein is commonly used to estimate protein content, amino acids are a better measure of protein quality. Amino acids are the building blocks of protein.

We looked at the amino acid levels of each of these forage types and their effects on horses.

Testing for amino acids 

  • We grazed six aged horses on cool-season grass (Kentucky bluegrass and orchardgrass mixture), legume (alfalfa) and warm-season grass (teff) pastures.
  • We took forage and blood samples before turning out the horses and again two and four hours following turn-out.
  • We looked at the nutrient and amino acid content of the forage and the amino acid content in the blood samples.



Authors: Krishona Martinson, Extension equine specialist, Michelle DeBoer, former graduate student,  Marcia Hathaway, professor of Animal Science, and Craig Sheaffer, professor of Agronomy and Plant Genetics, College of Food, Agricultural and Natural Resource Sciences; Kerry Kuhle, DVM; and Patty Weber, Michigan State University

Reviewed in 2021

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