Objective forage analysis methods ensure better nutritive content for horses.
Forages make up an estimated 50 to 100 percent of equine diets and are by far the biggest single component of most horses' daily nutritional intake in almost all areas of the country. In a hay-marketing survey published by Rutgers University Cooperative Extension, 93.5 percent of owners in New Jersey and Pennsylvania indicated that they fed hay all year long, with 61.5 percent purchasing it locally. The researchers involved with this study also found that hay quality was important to horse owners, since survey respondents had specific preferences for certain types and characteristics of the hay that they would select and buy (Photo 1).
Photo 1: The last few years in the Middle Atlantic and the Southeast were marked by an extreme drought and a lack of good hay. This past winter has been much wetter, and the 2010 hay crop promises to be one of the best in years. With so much hay available, horse owners should be able to select better quality hay at favorable prices.
This study, conducted in 1999 and repeated again in 2004, showed, however, that many of the criteria most important to owners did not correlate to the best means of evaluating hay. Owners rated freedom from mold, type of hay (timothy, orchard, alfalfa or various mixes) and absence of weeds as the three most important factors in hay choice. All these assessments were made visually without any type of analysis.
The reality is that hay is an important component of a horse's diet, but there are no standards, and there is little continuity in nutritional analysis of forage. Additionally, the method used by most owners to decide which hay to buy and feed is based largely on subjective criteria.
"It is incongruous that manufactured feeds must have a guaranteed nutritional composition, yet forages are bought and sold based on predominantly subjective measures," says Paul Sirois of Dairy One/Equi-Analytical Laboratories in Ithaca, N.Y., a company offering forage analysis for both dairy and equine clients. Sirois acknowledges that forage laboratory services across the nation have traditionally been there to meet the needs of the dairy industry, and the methods of evaluating hays have heavily favored ruminant nutrition demands. But laboratories have recently begun addressing the special problems of horses, trying to standardize equine forage nutritional analysis.
A large part of the driving force in this industry shift is the increased interest in carbohydrates (CHOs) in horse hay. CHO content has been implicated as a possible causative factor in equine disorders such as laminitis (see related story on p. 6E), Cushing's disease, equine metabolic syndrome and insulin resistance — all of which have been increasingly diagnosed in the last decade. Equine veterinarians have helped educate horse owners about the potential effects that hay quality and content can have on their horses' health. Now it is time to make better objective information available to those discriminating owners so that they can choose the best hay possible.
"Standardization of carbohydrate terminology is essential to fully understand the impact of CHOs on equine health and performance," Sirois says. Marketing of hay, from the viewpoint of both the buyer and the seller, would be greatly enhanced by providing nutritional information prior to its sale. "High-quality hay could be sold at a higher price, and specialty hay, such as low-CHO hay, would demand a premium," says Sirois.
Veterinarians can help this process by further educating their clients about better methods of hay evaluation and by encouraging more forage analysis within the horse-hay industry.
The simplest method of hay analysis is called the organoleptic or sensory method. It includes five categories, and each receives a certain percentage of points.
The important point, however, is that within a particular hay type, the stage of maturity at cutting is far more important to the quality of hay than when it was cut. "Typically, second-cutting hays in the Northeast and Middle Atlantic states are harvested at a more immature stage than first-cutting hays and under better harvest conditions," Sirois says. "It is these factors, rather than the notion of cutting that exerts an impact on final forage quality. High-quality grass hay contains few seed heads, high-quality alfalfa should not contain any seed pods and few blooms and high-quality clover should contain no mature, weathered flowers."
Mold and dust in hay can be a problem for all horses and a significant issue for sensitive individuals. It is estimated that one in six horses suffers from some type of allergic respiratory condition during its lifetime, and airway inflammation can severely affect performance and overall health. Many horse owners soak their horses' hay before feeding in an attempt to remove mold, dust and other allergic particles. New products are available that essentially steam clean entire hay bales, greatly reducing the amount of possible allergic particles. Good-quality, correctly cut, dried and baled hay should be free of dust and mold, but this new technology allows owners another way to help improve hay quality and assist horses prone to respiratory conditions.
Photo 2: The presence of seed heads and a high amount of stem indicates hay that was cut at a late stage of maturity. This field has passed the point of cutting for quality hay and will now produce rougher and steamier hay of lower nutritional value.
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.
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.
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.
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.