How do I interpret my horse hay analysis?

Bulk hay in storage

Oat hay stored in this hay barn was analyzed for this ask the expert question. New window.

Forage is the foundation of your horse’s diet. But do you know what it contains? Have it analyzed to remove the guesswork. If you purchase at least two or more months’ worth of hay at a time, it is worth doing. Your local county extension service may offer analysis services, or consider Equi-Analytical Laboratories for assistance.

Below are numbers taken from an actual hay analysis report. Let’s take a look at some of these key terms …

You’ll notice that the numbers shown in the above table are taken from the “As Sampled” column in the attached report. Reports provide you with two columns:  “As Sampled” or “Dry Matter.” This is because there is some moisture in hay (8.3% in this example), reflected in the “As Sampled” column. But if all the moisture were to be removed, the values would change, hence the “Dry Matter” column. When evaluating hay, I prefer to look at the “As Sampled” column because this gives you a realistic view of what your horse is actually consuming. The “Dry Matter” column becomes useful when evaluating pasture – to make the pasture comparable to hay, divide the numbers in the “Dry Matter” column by .90 to better compare them to hay with a moisture content of 10%.

Calories

Hay analysis reports describe calories as Digestible Energy. This is either in Megacalories (Mcals) per pound, or per kilogram. A megacalorie is equivalent to one million calories. In human nutrition, however, we say the word “calories” as a shorthand to denote a much larger, actual number – kilocalories (kcals). Looking at the example above, this hay provides .89 Mcal in one pound of hay. Comparing this to human nutrition where calories are expressed as kcals, it would be the same as 890 calories (less than a fast food hamburger).

Actually, the hay used in this example is somewhat higher in Mcals than most non-legume hay (hays other than alfalfa or other legumes). This is likely due to its higher carbohydrate level. The number of Mcals per lb (or per kg, derived by multiplying by 2.2), is an important factor in evaluating the suitability of the hay for your horse, especially if he is overweight. An overweight horse should have forage flowing through his digestive system at all times, but that forage needs to be low in Mcals in order for it to be fed free choice.

Evaluating protein

Oat hay was used for the above analysis. Oat hay, unlike hay made from grasses (e.g., orchardgrass, timothy, brome, Bermuda) or legumes (e.g., alfalfa, clover), tends to be of poor quality with a low crude protein percentage. The crude protein (CP) level, at only 5.7%, is considerably below the 8 to 10% CP average for most grass hays. Crude protein is 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). So to fix this particular hay, you would need to a considerable amount of alfalfa, or supplement with a high protein commercial preparation.

Lysine, one of 10 essential amino acids (those that cannot be produced and therefore, must be in the diet), is the only amino acid shown in most hay analysis reports. The average 1100 lb adult horse, at maintenance requires 27 grams of lysine at a minimum. The above hay offers only 0.20% -- low for most hays. If your horse were to consume 25 lbs of this hay, he would only receive 22.5 grams of lysine. Therefore, lysine supplementation would be advisable.

Digestible Carbohydrates

Non-structural carbohydrates (NSC) are calculated by adding Water soluble carbohydrates (WSC) to Starch. NSC is of particular importance to horses suffering from diseases/disorders that require a reduction in sugar and starches including metabolic syndrome (insulin resistance), equine Cushing’s disease, and polysaccharide storage myopathy. The %NSC should be below 12% to be considered safe to feed free-choice, and ideally below 10% (on an as sampled basis). Free-choice feeding of forage controls the hormonal response that occurs when a horse endures an empty stomach. This response keeps overweight horses overweight. Allowing continual grazing, 24/7, calms down stress hormones and allows the horse to burn fat. Test your hay first, to make certain it is appropriate.

WSC measures simple sugars and fructan levels. Simple sugars are digested in the foregut and raise insulin levels. Fructan, on the other hand, is digested in both the foregut and the hind gut, leading to a rise in insulin as well as the potential for endotoxins in the hind gut. Starch, the second component of NSC, is normally digested in the foregut down to individual glucose (blood sugar) molecules; therefore, it has a strong elevating effect on blood insulin levels. Since all three have the potential to significantly raise insulin levels, it is important to monitor these values for horses prone to insulin-related health problems.

Oat hay (and other hays from grain, such as rye, wheat, and barley) tends to be high in sugar and fructan, in preparation to produce the starchy seed. The hay evaluated in the above table is inappropriate for horses that need to regulate blood insulin levels. The percent WSC is 11.3% on an “as sampled” basis. Add this to the 7.7% starch, and you have a 19% NSC level, considerably above the 12% safety level. If this were the only hay available for your horses, it would either need to be soaked to remove excess sugars, or diluted with lower % NSC hay.

Ethanol soluble carbohydrates (ESC) and Non-fibrous carbohydrates (NFC) are not as useful to equine nutritionists. ESC is a subset of WSC, providing an idea of the simple sugars. Generally, the difference is attributable to fructan. NFC includes NSC (sugars, fructan and starch) plus pectin. Pectin is a water soluble fiber and does not contribute to insulin levels. Therefore NFC is not as useful as NSC.

Fibers

Fibers are technically classified as carbohydrates but the horse cannot produce the digestive enzymes necessary to break them down into small sugar units. Instead, the billions of bacteria living in the hindgut (cecum and large colon) are capable of producing digestive enzymes. Therefore, a healthy microbial population is important for your horse to derive calories from fiber. However, there is one type of fiber that is indigestible,  even by hindgut bacteria -- lignin. Lignin is increased as the plant matures.

Two numbers provide a measure of the fiber content in hay: Acid detergent fiber (ADF) and Neutral detergent fiber (NDF) measure fiber within the cell wall, with ADF a subset of NDF. Most hay will have an ADF level between 30 and 40% and an NDF level between 50 and 60% to be considered nutritious. If the levels go beyond these ranges, in indicates more lignin. This means that your horse is not able to thrive on this hay – it is not highly digestible and will end up in the manure. The above hay has acceptable ADF and NDF values. But if your hay does not, your horse will need to consume more to get the same amount of calories. 

Minerals

Many reports will provide common macro and micro minerals. Some key points…

Minerals and micronutrients

A low cost mineral block may be adequate to supply micronutrients if the forage is high quality and balanced. Ask an equine nutritionist for specific advice on your situation. New window.

Calcium to phosphorus ratio:

There should always be more calcium than phosphorus. Most hay (except much orchardgrass) will have this balance. The ideal ratio is 2:1, calcium to phosphorus, but the level of calcium can be even higher and still be considered safe. Notice in the above oat hay, the phosphorus level (0.19%) is dangerously close to calcium’s (0.22%). Adding alfalfa to the diet is a good idea for this hay to provide additional calcium (as well as protein).

Calcium to magnesium ratio:

Ideally, calcium content should not be more than twice that of magnesium. Most hays, even if the ratio is adequate, have a magnesium level that is lower than what horses ideally require for the nervous system and hormonal balance, since magnesium is poorly absorbed.

Potassium and sodium:

All hay is high in potassium and low in sodium. This is why it is necessary to have a supplement source of salt to provide additional sodium.

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. Notice in the example that iron is extremely high in relation to the other minerals. Most forages have high levels of iron. Therefore, iron does not need to be supplemented in the vast majority of cases. Copper, zinc, and manganese are very low and should be brought into balance.

Selenium:

Most analyses will not contain selenium values unless you specifically request it. It is worth analyzing, since selenium has a narrow range of safety. Too little can be just as damaging as too much, so know your hay’s selenium level before you supplement. In the above case, the selenium level is low. At only 0.03 mg/kg (ppm), 25 lbs provides 0.3 mg of selenium. Recommended ranges are between 1 and 3 mg selenium per day for most full-sized horses, and up to 5 mg per day for larger breeds or athletes.

Relative Feed Value (RFV)

RFV is an indication of the hay’s overall quality in terms of its digestibility and available nutrients. A value over 150 is ideal but few hays reach this level. Strive for an RFV of at least 100. This is an average score based on approximately 40% ADF and 50% NDF on a dry matter basis. The above example has close to 40% ADF, but almost 60% NDF (dry matter), which is reflected in its lower RFV of 91.

Bottom line…

All hay is dead. Once fresh pasture is cut, dried and stored, it starts to die and lose valuable nutrients. Mostly vitamins are lost because they are oxidized due to exposure to air, heat, light, and moisture, making a vitamin supplement necessary. Since hay is the basis of your horse’s diet, it is important to provide as nutritious a hay as possible that has adequate protein, balanced minerals, and is not overly high in sugar and starch. You cannot tell anything about the hay’s nutritional content by the way it looks, smells, or tastes. Analysis is the only way to know what’s in it – easy to do and well worth the reasonable cost.

Dig deeper^TM

See the actual hay analysis report the Dr. Getty analyzed. The hay analyzed is a dry-field oat hay, produced in Northern California.

Sampling and testing hay is relatively easy and can improve your horse's nutrition and avoid illnesses caused by deficient nutrition. You may enjoy viewing our How To Sample Hay slideshow that is related to this article.