Depending on where you have your hay analysis done, your result form may look a little different, but they should all contain the same basic information. Note that a hay test will provide information that relates to cattle that isn’t useful for horses, so only the values pertinent to equines are listed here:

Dry Matter (DM) – This refers to the percentage of dry material in your hay sample compared to its water content. When feed is offered to your horses, it will contain varying amounts of water – particularly between feeds such as pasture vs. hay. The dry matter will tell you how much of the feed is dry, and the remaining amount (100 minus DM) will be water.

You will also note that your results sheet will have a column for your other nutrients listed on a dry matter basis (nutrients in the feed assuming all water is removed) and for “as fed” or “as is.” The “as fed” column shows the concentrations of the nutrients in the sample with the water included, and represents what you would actually feed your horse. For example, in hay that is 90% dry matter and 10% water, it might have 15% protein on a dry matter basis, but only 13.5% protein on an “as fed” basis, because the feed is diluted by the water content. However, for pasture that might be 75% water and 25% dry matter, it could contain 15% protein on a dry matter basis, and just 3.75% protein on an “as fed” basis. Ideally, hay should be about 90% dry matter, with higher values of DM potentially indicating very brittle hay, while lower values (more moist) may increase the risk of mold.

Crude Protein (CP) – This refers to the protein content of the feed as a “crude” estimate. The analysis actually measures the amount of nitrogen in the feed (which is a component of protein) and uses that to estimate the amount of protein in the feed. Protein content in hay may range from 5-20% on a dry matter basis, depending on the type of hay – legumes such as alfalfa are higher, grasses such as timothy are lower – and stage of maturity of the plant when cut.

Many labs will also include values such as soluble protein or rumen degradable intake protein, which are more useful for ruminant diets such as in bovines – as horses don’t have rumens!

Acid Detergent Fiber (ADF) – This value represents a fraction of the fibrous component of the feed that contains cellulose and lignin. As cellulose is only moderately digestible because it is fermented by microbes in the large intestine, and lignin is indigestible even by microbes, the ADF fraction can be an indication of the digestibility of the hay. Higher amounts of ADF indicate the hay has lower digestibility and therefore also lower digestible energy. Ideally this fraction is less than 35% on a dry matter basis, although slightly higher values may be indicate a hay could be useful for an overweight horse or to help produce heat in the winter.

Neutral Detergent Fiber (NDF) – This value represents a fraction of the fibrous component that also includes a more digestible (fermentable by microbes) type of fibre – hemicellose, in addition to cellulose and lignin. This value is therefore higher than ADF, and can be used as an indication of palatability, with values ideally below 55%.

Ash – This is the component that represents the mineral content of the hay (see sidebar). Most labs will further analyze the hay for individual macrominerals such as calcium, phosphorus, potassium, magnesium, sulfur and sodium, which will be expressed as a percentage of the feed; as well as some trace minerals – iron, zinc, copper and manganese, which will be expressed on a parts-per-million (ppm) or mg/kg basis. Additional minerals such as selenium may be analyzed for an additional cost.

Crude Fat – This fraction represents the fat content of the horse’s diet, and is measured as the ether extract (EE = the part of a complex organic material that is soluble in ether and consists chiefly of fats and fatty acids.)

Digestible Energy – This value is calculated from other components of the diet to represent the calories in the hay (expressed as mcal/kg).

Non-Fibre Carbohydrate – Calculated from 100 minus % NDF minus % CP minus % crude fat minus % ash. Further simple carbohydrate fractions include starch, water soluble carbohydrates (WSC, which includes simple sugars and fructans), ethanol soluble carbohydrates (ESC, or simple sugars), or non-structural carbohydrates (NSC, which includes simple sugars, fructans and starch).

Why It Matters

Dry matter contains all of the nutrients; therefore, horses have to consume more of a wetter feed to receive the same amount of dry matter as they would from a drier feed. It is very important to know the dry matter content of a feed to establish feeding rates and insure that horses receive the proper amount of feed to meet their daily needs.

Crude Protein (CP) – Proteins are organic compounds composed of amino acids. They are a major component of vital organs, tissue, muscle, hair, skin, milk and enzymes. Protein is required on a daily basis for maintenance, lactation, growth and reproduction.

Acid Detergent Fiber (ADF) – Lignin is an indigestible plant component. As lignin content increases, digestibility of cellulose decreases, thereby lowering the amount of energy potentially available to the animal.

Fat – Fat is an energy-dense nutrient which contains 2.25 times the energy found in carbohydrates. Fat is added to rations to boost energy levels when intake may be limiting.

Ash is a measure of the total mineral content, which includes:

Calcium (Ca) – bone and teeth formation, blood clotting, muscle contractions, milk component, transmission of nerve impulses, cardiac regulation, activation and stabilization of enzymes.

Phosphorus (P) – bone and teeth formation, key component of energy metabolism, milk component, body fluid buffer systems.

Magnesium (Mg) – enzyme activator found in skeletal tissue and bone, neuromuscular transmissions.

Potassium (K) – osmotic pressure regulation and water balance, electrolyte balance, acid-base balance, enzyme activator, muscle contraction, nerve impulse conductor.

Sodium (Na) – acid-base balance, muscle contraction, nerve transmission, maintenance of body fluid balance, osmotic pressure regulator, cellular uptake of glucose, amino acid transport.

Iron (Fe) – hemoglobin and oxygen transport, enzyme systems.

Zinc (Zn) – enzyme activator, wound healing, skin health, immune system.

Copper (Cu) – required for hemoglobin synthesis, coenzyme functions.

Manganese (Mn) – growth, bone formation, enzyme activator, fertility.

Molybdenum (Mo) – part of enzyme xanthine oxidase, antagonistic and interactive effects with copper and sulfur.

Sulfur (S) – present in insulin, biotin, thiamin, heparin and chondroitin sulfate.

Chloride (Cl-) – acid-base balance, osmotic pressure regulation, component of gastric secretions.

Cobalt (Co) – required for vitamin B12 synthesis.

Selenium (Se) – component of glutathione peroxidase enzyme, antioxidant properties, prevention of white muscle disease and retained placenta.

Iodine (I) – essential for the synthesis of the thyroid hormones thyroxine (T4) and triiodothyronine (T3) that regulate basal metabolism.

Energy is the nutrient required in the greatest amount and is used in all biological processes including maintenance, growth, lactation, reproduction and activity level. Failure to supply adequate energy will result in poor performance.

Digestible Energy (DE) – the energy that is digested and absorbed by the animal – is determined by subtracting the energy contained in the feces from the gross energy. In horses, the fecal energy loss is typically 35-40% of the gross energy. The DE is used to balance the energy portion of the equine diet.

Non-Fiber Carbohydrates (NFC) – non-cell wall carbohydrates consisting of starch, sugar, pectin and fermentation acids that can serve as energy sources for the animal.

Source: Buckeye Nutrition