This is the time of the year that horse people should be making and/or buying their year's supply of hay. The moisture conditions have many concerned about drought conditions so it is even more important to get the year's supply of hay stored as soon as possible or to begin getting the supply.

What is "horse" quality hay? Horse quality hay is any hay that provides the horse the most nutrients, is free of mold and toxic weeds, is relatively dust free, the horse eats it, and the price is the lowest per unit of nutrient.

The reason a horse needs forage (grass or hay) is that it is a nonruminant herbivore. That is the horse was designed to consume and digest forages to supply nutrients (energy, protein, minerals, vitamins). The horse has a hindgut (large intestine) that contains a population of microrganisms, similar to the microrganisms in the cow's rumen, that breaks down plant (roughage) material that has not been digested by the enzymes of the small intestine. Because the horse's digestive system is designed as such it needs a certain minimum amount of "roughage" in the diet per day. Most equine nutritionists recommend that a horse consume at least 1% of its body weight per day in hay equivalent dry matter to maintain normal digestive system function. Another concern relating to normal digestive function and normal behavior associated with roughage and the fiber portion of the diet is that it appears a horse has a certain daily "chew factor". If a roughage source is fed as a pellet or chopped to a length of less than an inch the horse will not have to chew the roughage as long. Therefore less saliva is produced which has been shown to affect the ph (acidity) of the large intestine. It has been demonstrated that lowering the ph of the hindgut will affect the type of microrganisms present. In addition it is thought that when a horse's minimum daily "chew factor" is not met that the horse may begin to look to chew on other objects such as wood, manes, and tails. This may be due to too little fiber and the corresponding change in gut ph, boredom ( the horse simply may need to do something) or a combination of factors. Whatever the reasons it is important that the horse does meet its "chew factor" requirement.

The main nutrient supplied by hay to horses is energy. Energy requirements for the horse are expressed as megacalories of digestible energy. For example an 1100 pound horse being ridden lightly requires 20.5 megacalories of digestible energy per day. A high quality Costal Bermudagrass hay as shown in Table 1 will contain 0.9 megacalories of digestible energy per pound on a 100% dry matter basis. If the hay is 90% dry matter that means that as the hay is fed out of the bale it will contain 0.81 megacalories of digestible energy per pound. Therefore to meet the 1100 pound horse's energy requirements being ridden lightly the horse would need to consume 25.3 pounds of hay. A horse can consume up to 2.25 to 2.5% of its body weight in forage dry matter per day.

The problem of determining hay quality for horses based on energy content of the hay is that routine laboratory analyzes do not provide digestible energy values. Instead a typical routine forage analysis will provide crude protein, neutral detergent fiber, crude fiber, moisture, and possibly some mineral analyses. It is well documented that as a plant matures crude protein values decline and fiber values increase. Along with the advancing maturity of a plant the digestibility decreases and therefore the digestible energy value decreases. Therefore the higher the neutral detergent and crude fiber values the lower the digestible energy values.

I have attempted to simplify all of the above by putting "Relative Feed Values" on various types of horse hays fed in the southeastern United States. Most all hays are compared to alfalfa so I have put a relative feed value of 100 on a high quality alfalfa. I have listed three levels of relative feed values as well as digestible energy values for each type of hay so that there are three categories into which a hay may fall; excellent, average, and poor quality. Of course this table is useless unless the hay is analyzed for at least dry matter, crude protein, neutral detergent fiber and/or crude fiber.

Table 1. Approximate digestible energy and relative feed values of hays for horses.  (100% Dry Matter Basis)