by Dr. Marty Adams – Equine Nutritionist for Southern States
Horse owners are aware of the importance of fiber in their horse’s diet, as they know the benefits of feeding enough good quality hay or pasture. But they may not be aware of the fiber values and guarantees in horse feeds.
Crude fiber has been used as an estimate of the fiber content of feeds, and is one of the required measurements used in a guaranteed analysis of nutrients that is legally required for all livestock feeds, including horse feeds. Crude fiber is required as a maximum guarantee, to prevent the addition of an excessive amount of fibrous ingredients to a feed, which would be a disadvantage with most livestock feeds as it would lower the energy content. As crude fiber content of a feedstuff increases, the energy content or calories per pound is deceased. This allows comparisons to be made between competitive feeds where energy content is a major consideration.
Crude fiber is not a real accurate measure of the total fiber of a plant or animal feedstuff. A test for crude fiber measures most of the cellulose and some of the hemicellulose and lignin, which are the three components of the plant cell wall or the total fiber fraction. Neutral Detergent Fiber (NDF) is another chemical test that measures the total amount of plant cell wall or fiber (cellulose, hemicellulose and lignin). It is a more accurate measure of total fiber and is negatively correlated with forage intake in the horse. As NDF content of a feedstuff increases, intake deceases, and NDF is used to compare hay quality. Acid Detergent Fiber (ADF) is another chemical test used to evaluate fiber quality. ADF measures the amount of cellulose and lignin, which are the least digestible components of the plant. ADF is negatively correlated with forage digestibility, as ADF increases the digestibility and energy content of the feedstuff decreases. ADF can be used to compare hay quality and also fiber quality of horse feeds, and the ADF value can be included in an equation to estimate digestible energy content of forages and feeds for the horse.
The American Association of Feed Control Officials has recommended that legally required nutrient guarantees for horse feeds include ADF and NDF values. This provides more information to horse feed customers and allows them to make more informed decisions when it comes to purchasing horse feeds and supplements.