Common Hay: A Quick Comparison

Six indicators to look at when deciding which hay is best for a mature horse:

1) Digestible Energy (DE) is an estimate of energy that is digested and absorbed by the horse. The DE is helpful when determining how much energy a hay contributes to the overall diet. Energy requirements can be expressed as megacalories (Mcal) per lb or kilocalories (Kcal) per lb. One Mcal is equal to 1,000 Kcal, so make sure you are comparing apples to apples when comparing DE amounts.

2) Crude Fat (CF) is an estimation for the fat content of a feed. Fats contribute energy to the diet. Fat is a very energy-dense nutrient and contains 2.25 times the energy found in carbohydrates.

3) Nonstructural Carbohydrate (NSC) is the term used to describe the sugar and starch content of the hay. This is an important number to know if you are dealing with a horse that is sensitive to sugar and starch.

4) Relative Feed Value (RFV) is an index for ranking forages based on digestibility and intake potential. RFV is calculated from ADF and NDF (see below). An RFV of 100 is considered the average. The higher the RFV, the better the quality of the hay. RFV values should not be used for making direct comparisons of forages. Rather, a range of RFV values should be used to classify a forage. For example, if an RFV of 150 is the target value, any forage testing between 145 to 155 should be considered to have an equivalent value. A good rule of thumb is to accept anything within at least +/- 5 points of the target value.

Neutral Detergent Fiber (NDF) explained: NDF is a measure of the fibrous portion of the forage, also known as structural carbohydrates. They give the plant rigidity, enabling it to support itself as it grows. The higher the NDF the more course (stemmy) and unpalatable the hay will become.

Acid Detergent Fiber (ADF) explained: ADF is a measure of cellulose and lignin. Cellulose digestibility is negatively influenced by the lignin content. As lignin content increases, the digestibility of the cellulose decreases. The higher the ADF, the less digestible the hay will be.

5) Crude Protein (CP) is the total protein found in the plant, which includes true protein and non-protein nitrogen. The percent protein a horse needs depends mostly on his age and reproductive status, as young growing horses or mares in late pregnancy have the highest protein requirements. Mature horses, even when in hard work, have lower protein requirements.

6) Calcium (Ca) and Phosphorus (P) are two minerals that must be balanced in a horse’s diet to ensure proper bone development. Hays typically contain more calcium than phosphorus. It is important to know how much calcium and phosphorus the hay is contributing to the overall diet. A healthy diet will provide calcium and phosphorus in a 2:1 ratio.

Of course, the best way to find out what nutrients your hay is contributing to the diet is to have it tested. Contact your local cooperative extension office for advice on how to properly collect a hay sample and the name of a testing facility near you. Or visit Equi-Analytical for instructions on sampling and how to submit a sample for testing.

Below is a chart that will give you an idea of what the different types of hay contribute to a horse’s overall diet.



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