hay analysis

So you took steps to get your hay crop analyzed. That’s good. But what do the results mean for your horse?

Your horse’s hay should be a nice green color, smell fresh and be free of dust and mold. It should also be soft – not too coarse or filled with too many stems. But outward appearances tell you nothing about the hay’s nutritive value, and that creates a lot of guesswork when it comes to determining the quality of your horse’s die.

The only way to know what your horse is consuming is to have your hay analyzed. This may not be feasible if you buy a new batch of hay every few weeks. But if you have at least two months of hay on hand, it is well worth having it analyzed by a reputable lab. Your local extension service may offer analysis services, or consider Equi-Analytical Laboratories. Regardless of the lab you choose, however, be sure the hay is evaluated for horses – if it’s evaluated for cattle, several key indicators may not be included in the report.

Common Terms and What They Mean

Crude protein (CP) – This is an estimation of total protein based on the quantity of nitrogen in the hay. It does not tell you anything about the amino acid composition or the protein quality. To create a high quality protein, one that will help your horse maintain and repair tissue, combine a grass hay with a lesser quantity of a legume (typically alfalfa). Most grass hay contains 8% to 10% CP, whereas legumes (alfalfa, clover, perennial peanut) can range from 17% to 20%. Grain hays (oat, wheat, rye) generally have a lower CP than grass hay.

Acid detergent fiber (ADF) and neutral detergent fiber (NDF) – Both these measure fiber content. Since fibers are digested by the microbes living in the hindgut (cecum and large colon), a healthy microbial population is important so your horse can derive calories from fiber. However, one type of fiber is completely indigestible – lignin. Lignin increases as the plant matures. The higher these two values, the more lignin the hay contains. This means your horse is not able to thrive on this hay since much of it ends up in the manure. The ideal ADF is less than 31%; the ideal NDF is less than 40%. However, most hays have values 10 or more points above these desired levels. To compensate, more hay needs to be consumed. This can be easily solved by allowing your horse to have free access to hay 24 hours a day.

Non-structural carbohydrates (NSC) – This represents the total amount of sugar, starch and fructan in the hay. To obtain %NSC, add %WSC (water soluble carbohydrates) and %Starch (see next page). If your horse needs a low sugar/low starch diet, the %NSC should be less than 12%.

Water soluble carbohydrates (WSC) – This measures simple sugars and fructan levels. Simple sugars are digested in the foregut and raise insulin levels. Too much can lead to laminitis because of elevated blood insulin. Fructan, on the other hand, is digested in the hindgut. Too much can result in laminitis caused by endotoxins in the bloodstream. Ethanol-soluble carbohydrates (ESC) – It’s a subset of WSC that gives you a better idea of the simple sugar level. WSC minus ESC provides a fair measurement of fructan levels.

Starch – Starch is normally digested in the foregut down to individual glucose (blood sugar) molecules. Therefore, it has a strong elevating effect on blood insulin levels.

Know Your Minerals

Calcium to phosphorus ratio – Hay should contain more calcium than phosphorus. Most hay (except orchard grass) will have this balance. The ideal ratio is 2:1, but the level of calcium can be even higher and still be considered safe. The phosphorus concentration must never be higher than the calcium levels.

Calcium to magnesium ratio – Ideally, calcium content should not be more than twice that of magnesium. Most hays have a magnesium level is lower than what horses ideally require, and that magnesium is not well absorbed.

Iron, zinc, copper and manganese – Ideal ratios are iron:copper 4:1; copper:zinc:manganese 1:4:4. However, keep in mind that minerals interact with one another, interfering with absorption. Therefore, be conservative when supplementing minerals if your hay is close to these ideal ratios. And since most hay is very high in iron, additional supplementation of this mineral is not only unnecessary, but can be problematic for the insulin resistant horse.

Selenium – This mineral is worth analyzing, since selenium has a narrow range of safety. Too little can be as damaging as too much, so know your hay’s selenium level before you supplement. Strive for a range between 1 and 3 mg of selenium per day for the average sized horse at maintenance, and up to 5 mg per day for a larger breed or one that is exercised heavily.

Quality and Quantity

Since hay is such a key component of the horse’s diet, it needs to be of high quality. Quality is determined by not only the color and condition of the hay, but the protein, sugar, starch, fiber and mineral levels, as discussed above.

Notice that vitamins were not included in this list – that’s because when fresh grass is cut, dried and stored to make hay, many key vitamins are destroyed (including vitamins C, D and E, as well as beta carotene, which is used to make vitamin A). In addition, Omega-3 fatty acids are virtually nonexistent in hay. Therefore, it is important to fill in these gaps through proper supplementation.

A horse’s digestive tract is designed to have forage flowing through it at all times. There are many reasons for this – it keeps the stomach continually producing acid, maintains a healthy hindgut microbial population, and ensures the digestive tract muscles are moving. Hay and/or pasture fulfill this need, thereby preventing common disorders such as colic, ulcers, diarrhea and laminitis.

Bottom line – know what is in your horse’s diet! Since horses typically eat the same thing day after day, it is critical to feed a forage source that’s both digestible and nutritious. Analysis is the only way to accurately know the value of your hay. It’s inexpensive and easy to do, and is a worthwhile tool for keeping your equine friend healthy.

Juliet M. Getty, PhD is a consultant, speaker, and writer in equine nutrition. A retired university professor and winner of several teaching awards, Dr. Getty presents seminars to horse organizations and works with individual owners to create customized nutrition plans designed to prevent illness and optimize their horses’ overall health and performance. Based in beautiful rural Bayfield, Colorado, Dr. Getty runs a consulting company, Getty Equine Nutrition, LLC (GettyEquineNutrition.com), through which she helps horse owners locally, nationally and internationally. The well being of the horse remains Dr. Getty’s driving motivation, and she believes every horse owner should have access to scientific information in order to give every horse a lifetime of vibrant health.


Dr. Juliet M. Getty earned her Master of Science degree in Animal Nutrition at the University of Florida. She completed her doctoral coursework in Animal Nutrition at the University of Georgia, and continued her studies at the University of North Texas, where she earned her PhD. Winner of several teaching awards, Dr. Getty has taught comparative nutrition studies at the University of North Texas for 20 years. At the same time, she has been working in the field, consulting privately with horse owners to customize feeding plans that address a variety of health conditions. Recently retired from academia, she now resides in Denton, Texas, where she devotes herself full-time to equine nutrition. Through her consulting company, Getty Equine Nutrition, she provides consultations locally, nationally and internationally.