Choosing the Right Hay for Your Horse

Edward Dunphy

Choosing the Right Hay for Your Horse

The time of harvest relative to the stage of plant maturity can affect the crude protein and digestible dry matter of hay. In general, crude protein and digestible dry matter decrease as the plant matures.  Sometimes your nutritionist will refer to other measures of digestibility (another way of saying how many calories are available to the animal), such as “digestible energy” or even “NDF (Neutral Detergent Fiber).”  No matter what measure you use, the result is the same.  The more mature the plant is at harvest, the lower the amount of energy (calories) provided by the hay.

The following chart, from an article Prepared by Marvin H. Hall, Assistant Professor of Agronomy, Penn State, and Jerry H. Cherney, Associate Professor of Agronomy, Cornell University, shows this relationship.

Chart of Nutritional Value of Perennial Cool Season Forage Based on Stage of Harvest

If you look at Timothy in the above chart, you will see the digestible dry matter gets lower as the plant matures.  If we were looking instead at NDF, you would find the numbers getting higher as the plant matured.  The result is fewer calories available to the horse from each flake of the more mature hay.

The same can be said for crude protein.  The more mature the plant is, the lower the amount of protein provided by each flake of hay.  It should be no surprise that prejoint harvested hay is so high in protein.  This would be equivalent to new spring grass!

The graph below from “Selecting Quality Hay for Horses” by Mark A. Russell, Department of Animal Sciences and Keith D. Johnson, Department of Agronomy, Cooperative Extension Service Purdue University tells the same story.

Graph showing how maturity of grass at harvest effects crude protein and digestible energy

This graph (Figure 2) gives a pictorial view of the different stages of orchardgrass and shows way various plant nutritional components increase or decrease.  It is from “Controlled Grazing of Virginia Pastures by Harlan E. White and Dale D. Wolf, Extension Agronomists, Forages, Crop and Soil Environmental Sciences Department, Virginia Tech.  Increases in Lignin as the plant matures means that the plant is becoming less digestible while the available protein decreases.

Chart shows change in nutrients in orchardgrass at various stages of growth


The issue then becomes “what hay is right for your horse?”  That all depends on what your horse’s daily calorie and protein requirements are.  Shelby Baughan, the CFC Farm & Home Center Equine Specialist, can help you determine that.  Breed, life stage, and activity level all play into the answer to this question.  Once you know what caloric and non-caloric nutrients the hay you own or intend to purchase is contributing to the equine diet, an appropriate supplemental feed can be chosen to balance the remaining requirements.