You’ve just tucked a couple of month’s supply of hay into your barn—or maybe an entire season’s worth—and now it’s time to get acquainted with it. You made sure it was green and attractive, fresh-smelling and free of mold. You’ve stored it under cover and away from the incursion of any damaging moisture. Now you’re ready to find out what it offers your horse in the way of nutritional value.

Keep in mind that when you take fresh, healthy pasture and you cut it, dry it, and store it to make hay, it loses most of its vitamin content as well as its omega 3 and omega 6 fatty acids. It no longer has vitamins E, C, D or beta carotene (which is used to make vitamin A). Therefore, if the horse is getting predominantly hay and is not getting a commercial feed fed according to directions, then you really need to supplement the diet with a good vitamin/mineral supplement. But you’ll want to know what’s in your hay before you start making up for what’s not.

Hay analysis gives you the starting point from which to evaluate and balance your horse’s whole diet. If you purchase at least two or more months’ worth of hay at a time, it is worth having it analyzed. Your local county extension service may offer analysis services, or consider sending a sample to Equi-Analytical Laboratories (www.equi-analytical.com). Follow their directions for selecting and submitting samples.

What does the hay analysis tell you? Typically, it will return the following information:

Crude protein (CP)—an estimation of total protein based on the amount 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 amount of a legume (typically alfalfa). Most grass hay contains 8-10% CP, whereas legumes (e.g., alfalfa, clover, perennial peanut) can range from 17-20%. Grain hays (oat, rye) generally have a lower CP than grass hay.

Acid detergent fiber (ADF) and Neutral Detergent fiber (NDF)—both measure fibers (there are five types). Since fibers are digested by the microbes living in the hindgut (cecum and large colon), a healthy microbial population is important to allow your horse to derive calories from fiber. However, there is one type of fiber that is indigestible—lignin. The lignin ends up as manure. Lignin content increases as the plant matures. The higher these two values (ADF and NDF), the more lignin the hay contains and the less likely that your horse can thrive on this hay. The ideal ADF is less than 35%; ideal NDF is less than 45%. However, most hays have values 10 points or more higher than 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)—total amount of sugar, starch and fructan. To obtain the percentage of NSC, add together the percentage of WSC (water soluble carbohydrates) plus the percentage of starch. If your horse needs to have a low sugar/low starch diet, the percent of NSC should be below 12%.

Water-soluble carbohydrates (WSC)—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, for the most part, is digested in the hind gut, although some shorter chain fructose molecules can contribute to elevated insulin. Too much fructan generally results in laminitis caused by endotoxins in the bloodstream.

Ethanol-soluble carbohydrates (ESC)—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—normally digested in the foregut down to individual glucose (blood sugar) molecules; therefore, it has a strong elevating effect on blood insulin levels.

Minerals—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.

• Calcium to phosphorus ratio There needs to be more calcium than phosphorus in hay. 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. Phosphorus concentration must never be higher than calcium levels.
• Calcium to magnesium ratio Ideally, calcium content should not be more than twice that of magnesium. Most hays have a magnesium level that is lower than what horses ideally require. Furthermore, magnesium is not well absorbed, so supplementing may be suggested.
• Iron, Zinc, Copper, and Manganese Ideal ratios are Iron:Copper 4:1; Copper:Zinc:Manganese1:4:4.
• Selenium This is worth analyzing, since selenium has a narrow range of safety (1 to 5 mg per day). Too little can be just as damaging as too much, so know your hay’s selenium level before you supplement.

Feeding your horse like a horse—the way nature intended—means feeding the most nutritious diet possible, including giving him hay free choice to mimic his natural grazing pattern. You’ll be more confident in feeding this way when you get to know your foundation element—the hay—through a laboratory analysis.

Juliet M. Getty, PhD, is an internationally respected equine nutritionist available for private consultations and speaking engagements. Getty is the Contributing Nutrition Editor for the Horse Journal and she will be speaking at Equine Affaire in Massachusetts on Nov. 7-10, 2013. Her comprehensive reference book, Feed Your Horse Like a Horse as well as all the books in her “Spotlight on Equine Nutrition Series,” are offered for purchase through her website and at Amazon.com. In fact, there’s a lot going on at www.gettyequinenutrition.com: sign up for Getty’s informative—and free—monthly newsletter, Forage for Thought; read articles and search her nutrition forum; and purchase previously recorded teleseminars in audio format or in print through the Spotlight series. Contact Dr. Getty directly at gettyequinenutrition@gmail.com.