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A better way to evalute hay
Objective forage analysis methods ensure better nutritive content for horses.


DVM360 MAGAZINE


  • Color (10 percent) is important to owners but is generally overrated. Most good hay is a bright natural green to green-yellow (Photo 3). In general, the more yellow a hay is, the more mature it is. Hay that has been rain-damaged (dark-brown or black with brittle stems), sun-bleached (yellow and brittle), heat-damaged (brown and musty smelling) or moldy will be off color. Good hay should smell clean and slightly sweet. "Odor is the primary reason for animal rejection, and most horses smell their hay before eating it," Poole says. Yet many owners either fail to pay attention to hay smells or are just not that sensitive when evaluating good from bad odors.
  • Foreign material (10 percent), the last category for hay evaluation, includes weeds (thistle, pigweed and nettles), insects (blister beetles), trash or other objects. Looking at and handling the hay can provide a good assessment of the amount and type of foreign material present.

More objective methods


Photo 3: Good drying days lead to good-quality hay that is light-green in color, slightly sweet smelling and free of dust, mold and foreign material. But only chemical analysis can truly evaluate quality and give an owner an idea of the digestibility and carbohydrate content of hay.
While this sensory method of evaluation can often provide useful information on hay quality, there has been a need for more objective nutritional data. The evolution of forage analysis has a long history. In 1860, Henneberg and Stohman developed a method of chemical feed analysis. Their Proximate Analysis method divided all feed into six fractions — water, ether extract, crude protein, ash, crude fiber and nitrogen-free extract. This analysis was not useful, however, because it made no determination of how digestible any of the fractions were.

More recently, the Van Soest Detergent Analysis method separates the dry matter of forage into either cell walls or cell contents. Cell contents consist of sugars, starches, soluble CHOs, pectin, protein, nonprotein nitrogen, lipids and water-soluble vitamins and minerals that are all (98 percent) digestible. Cell walls consist of cellulose and hemicellulose, which are digestible by the horse, and other indigestible components. This analysis yielded the current system that reports crude protein, neutral detergent fiber (NDF; the portion of the forage that is composed of cell walls) and acid detergent fiber (ADF; the portion of NDF that is indigestible). High-quality hay should have low ADF and low NDF values, indicating that the indigestible portion of the hay is small. By adding CHO evaluation to hay analysis, one more important factor that can possibly influence an owner's purchasing decisions has been provided.

In 1995, a method for determining nonstructural CHO was introduced that identified sugars as water-soluble carbohydrates (WSC). This WSC fraction contained monosaccharides, disaccharides, oligosaccharides and polysaccharides. The polysaccharide of greatest importance in horses is fructan, which is a plant storage CHO found primarily in cool season grasses and is directly related to many equine metabolic conditions. Even more advanced analysis currently adds the WSC to the starch component of forage, producing a value called nonstructural CHO (NSC). Being able to identify and quantify fructan in forage samples and to determine the amount of sugar and starch (NSC) allows owners to more carefully select hays for sensitive individuals and horses that cannot tolerate high CHO levels.

Encouraging the move toward objectivity

Forage analysis can quickly become an alphabet soup of values — CHO, WSC, NDF, ADF, NSC — but it will benefit equine veterinarians to understand these terms and to help push for better, more standardized hay analysis. Encouraging clients to use objective analysis for forage purchases will reward those producers baling good-quality hay and will help move the industry forward. Performance horse owners needing high-energy hay will be able to purchase it, and those needing low-CHO hay for a horse with laminitis or Cushing's disease will also be able to find it.

While it will always be important to touch and smell the hay fed to horses, objective analysis is truly the future for an age-old industry.

Dr. Marcella is an equine practitioner in Canton, Ga.


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Source: DVM360 MAGAZINE,
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