Hay Quality for Horses

Apr 05, 2019

Hay Quality for Horses
Why should horse owners be concerned about hay quality for their horses? Horses need to be fed at least one percent of their body weight daily (dry matter) as forage.

Most horses are fed more than that — many receive two or more percent of their body weight per day in grass or hay (on a dry matter basis). This means that a 1000-pound horse may easily eat 15-20 pounds of hay per day, along with 3–6 pounds of a concentrate ration. When problems occur that may relate to nutrition, horse owners usually look at the concentrate portion of the diet. However, when the vast majority of the horse’s diet is hay or grass, we also need to pay attention to the important role that forage plays in the horse’s total nutrient status. The quality of the hay greatly dictates the nutritional value.

There are several factors that affect the hay quality, and therefore the nutrient content. The higher the hay quality, the better the horse’s digestive tract is able to digest and absorb the nutrients contained in the hay. 

The factors that affect the quality of the hay include maturity at time of harvest, plant species, fertilization, season at which hay is harvested, climate conditions, storage conditions and age (time since cutting). The maturity of the plant at time of harvest has more impact on the hay quality than any other factor. Young, leafy, immature plants contain more protein, energy and minerals than older, stemmier plants. As a plant matures, it contains more fiber (and a higher concentration of lignin, which is indigestible), therefore is overall less digestible for the horse, as well as containing less protein, energy and minerals. To ensure high-quality hay, plants should be harvested at the proper stage of maturity; for instance, timothy should be cut in the pre-bloom or early-bloom stage for the highest nutrient content.  

Plant species (e.g., grass versus legume) has an impact on the nutrient content of the hay, but not to the extent that most horse owners believe. The maturity of the plant when it was cut has much more influence, because plant cell walls become more lignified as the plant matures, so a mature plant contains more indigestible fiber than an immature plant. Alfalfa tends to have more protein, energy and calcium than grass hays, but research has shown that a high-quality grass hay may provide more nutrients than a medium- or low-quality alfalfa because the higher-quality grass hay is less fibrous and therefore more digestible. For example, for protein to be of value to a horse in providing essential amino acids, it must be digested and absorbed in the horse’s small intestine. Since the fiber in hay is digested through fermentation by the microbial population in the horse’s cecum and large intestine, the higher the fiber content in the hay, the more of the hay that will pass undigested through the upper gut, thus much of the protein will not be available for digestion until the digesta has already passed through the small intestine. Horse owners sometimes feel that alfalfa is always a better choice for horses than grass hays, but that is not necessarily true. Even if an alfalfa hay analyzes higher in protein and other nutrient content than a grass hay, that alfalfa may not provide more nutrition to the horse.

Fertilization primarily affects yield per acre rather than nutrition of any one bale of hay. The season at which the hay is harvested affects quality — digestibility is highest for forages harvested in the spring, somewhat lower in mid to late summer, and then it rises again slightly in autumn. Climate conditions, such as excessive moisture or drought can affect the quality of hay, especially since climate conditions can affect when the hay is cut. Often the plants become more mature than optimum because climate conditions are not conducive to harvesting at the best time.

Storage conditions and age (time since cutting) primarily affect vitamin content of hays. Many vitamins, such as vitamins A and E, are not stable over time and lose biological activity. Environmental conditions such as heat, sunlight and rain can hasten the loss of vitamin activity in hay. 

When evaluating hay, there are some simple characteristics that indicate appropriate maturity of plants, including:
  • High leaf-to-stem ratio
  • Small diameter stems
  • Few seed head or blooms
Other factors to look for include:
  • Fresh smell and appearance
  • Cleanliness (no dust, mold, weeds or trash)
  • Color (a faded, yellow or brown color may indicate aged hay or poor storage conditions)

Find the hay that is soft and pliable, and feels good when you squeeze a handful. If it feels like you’re squeezing a handful of sticks, that’s not a good choice of hay to feed your horse. Not only will poorer quality hay provide less nutrition for your horse, but as hay quality decreases, a horse’s voluntary intake is also reduced.

When good quality hay is scarce, or consistency of nutrients is critical, a complete feed such as Purina® Equine Senior®Equine Adult® or Equine Junior®Omolene #400®, or Impact® Senior or Impact® Hay Stretcher are excellent options to replace some or all of the hay in your horse’s diet.

--Purina Animal Nutrition

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