Claims that alfalfa hay's high protein and calcium concentrations contribute to developmental orthopedic disease (DOD) in young horses may just be an old wives' tale, reports Anne Rodiek at the 2004 National Alfalfa Symposium and 34th California Alfalfa Symposium held last month in San Diego.

The link between DOD and alfalfa hay is refuted by research findings, although Internet sites and misinformed horse owners and professionals continue to believe the opposite, Rodiek says.

Statistics on horse numbers and hence the potential alfalfa hay market for horses are difficult to establish, but Rodiek says the American Horse Council estimates there are 6.9 million horses in the U.S. California ranks as the second largest horse state in the nation where Rodiek estimates there are 625,000 horses that could eat as much as 2.5 million tons of hay per year.

It is incumbent upon alfalfa growers and hay suppliers to educate horse owners about the nutrient content and characteristics of hay to help them make the right nutritional decisions for their horses, says Rodiek, who serves as professor, Department of Animal Science and Agricultural Education, California State University, Fresno.

Research has not addressed most of the claims against alfalfa hay for horses, Rodiek says. But some of the allegations against alfalfa hay have been refuted. Alfalfa hay's high protein and energy values support growth to a greater extent than comparable amounts of grass hays. Its excessive levels of protein and calcium (compared to nutrient requirements of the horse) have not been implicated as agents for DOD. And while alfalfa hay is higher in digestible energy than grass hays, its nonstructural carbohydrate composition is low compared to concentrate feeds (and relatively lower than grass hay), and the blood glucose response it produces is similarly low.

Diets research finding

Rodiek says an examination of research on growth and growth disorders shows that diets that exceed the energy requirements of growing horses by approximately 30 percent have been shown in some, but not all studies, to increase the incidence of DOD in growing horses. Not just the amount, Rodiek reports, but the type of energy in the diet and the management of feeding may be factors that can increase orthopedic disease. For instance, in nature horses graze almost continuously on high water, nutrient dilute pastures. But in confinement, horses are often fed meals twice or three times daily of grain rich diets. The effect of “bolus” consumption of high starch diets causes large fluctuations in blood concentrations of glucose and insulin. These fluctuations, Rodiek says, are thought to influence cartilage and/or bone development by influencing secretion and circulating levels of growth related hormones, such as thyroid- and growth-hormones and insulin-like growth factor.

Rapid growth, in general, appears to be associated with DOD. And although dietary protein is essential for optimal growth of the horse, neither high nor low dietary protein content has been implicated directly in DOD. Similarly, although imbalanced calcium and phosphorus ratios have been blamed for abnormal bone growth, research has not produced clear evidence that excess calcium or marginal phosphorus cause DOD.

Magnesium, also, has not been implicated in causing growth disorders, although very high levels may inhibit copper absorption and low levels of copper have been shown to be associated with a higher incidence of DOD.

All of this exonerates alfalfa hay as forage for growing horses, Rodiek reports.

California horse people are divided in their opinions about the value of alfalfa hay for horses. Rodiek says some recognize it as a rich source of protein and calcium and a good source of energy compared to other forages. Some horses are fed only alfalfa hay with no apparent ill effects. Yet other horse owners feel strongly that alfalfa hay is imbalanced in its nutrient composition compared to the nutrient requirements of the horse and should be fed alfalfa sparingly or not at all.

Rodiek says that horse owners are devoted to the well-being of their horses and will spare little expense to ensure their well being. However, horse owners are not always educated about nutrition. As a result, the only source of nutrition information for horse owners are often feed store personnel and magazine ads.

“What can a hay producer say to a horse person? Well you can tell a horse person that protein is not the same as energy. A lot of them have that confused.”

Rodiek suggests asking them what they think their horses need. “Most of them will say, well, I want them to eat it, I don't want them to be bored, and I want them to meet their energy requirements.”

She suggests that alfalfa producers/suppliers explain energy contents. “If you say that alfalfa hay is 1.2 mega calories per pound of digestible energy and grass hay has .9, then you can talk to them and say that legume hays are about 20 to 30 percent higher in energy.” As you continue your education of the horse owner, Rodiek says, you can then determine from the horse owner how much time they want their horse to spend eating. Determine from them what their actual need for energy is versus entertainment, and get them to talk about what they use their horse for. “Then you can start talking to them — in their own terms and at their own level — about what hay would best meet their horse's needs,” Rodiek says.

Additional points suggested

Rodiek suggests making the following additional points when talking to and selling alfalfa hay to horse people:

  • Alfalfa hay, despite its excess protein and calcium content (compared to nutrient requirements), has not been implicated directly as causative of developmental orthopedic disease in growing horses.

  • Grass hay is lower in energy and protein and higher in fiber than legume hay. It is frequently more variable in quality and palatability than legume hay.

  • Grass hay is lower in non-fiber carbohydrate but higher than nonstructural carbohydrate (sugars and starches) than legume hay, particularly oat hay.

  • For horses that are overweight, laminitic or prone to metabolic disease, keeping nonstructural carbohydrate content of the diet low may be important. For this purpose, Bermudagrass may be more suitable than oat hay. Alfalfa hay may also be useful to these horses.