12/14/2025
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Horses are foragers and grazers by nature. Their digestive systems and physiology are best suited to continuous intake of relatively low-energy, high-fiber grasses, such as timothy, orchard grass, Bermuda grass, or teff. These forages support gut motility, proper microbial fermentation, and healthy connective tissue (fascia) function without overloading the system with concentrated nutrients.
Alfalfa, by contrast, is a legume โ the same botanical forage family as clovers and sainfoin. Legumes are fundamentally different from grasses in nutrient composition: they are higher in protein, energy, calcium, and magnesium than grass hays. This richness can pose concerns.
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Why Alfalfa Is Different from Grass
1. Nutrient Density
Alfalfa contains significantly more protein, energy, and calcium than most grass hays. For example, alfalfa protein often ranges well above 15โ18%, whereas grass hays usually fall in the 7โ12% range. Calcium in alfalfa can be 4โ5 times higher than grass hay.
horseracingsense.com
2. Calcium-Phosphorus (Ca:P) Imbalance
Horses require a balanced Ca:P ratio โ ideally about 1.5:1 to 2:1 for growth and body maintenance. Alfalfa often has a Ca:P of 4:1 to 6:1 or greater, which can lead to reduced phosphorus availability and mineral imbalances. Prolonged imbalance, especially in young horses, has been linked to poorer bone development. horseracingsense.com
3. Grass vs. Legume Digestibility
Research shows that horses fed alfalfa absorb more calcium and magnesium than when fed grass hay, due to alfalfaโs higher mineral availability. However, the overall nutrient density significantly exceeds maintenance needs for horses.
PubMed
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Who Legumes Are โDesignedโ For
Legumes like alfalfa, clovers, and sainfoin evolved to support ruminant animals (e.g., cows, goats, sheep) with multiple-chambered stomachs capable of fermenting very high protein and mineral forages. These species efficiently use the rich protein and calcium, often for rapid growth and lactation.
Horses, however, are non-ruminant hindgut fermenters. They do not metabolize these high concentrations in the same way, and feeding straight legumes without careful balancing can lead to unintended metabolic outcomes.
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Concerns with Regular Alfalfa Feeding
1. Excess Protein Intake
Alfalfaโs high protein exceed a horseโs actual requirements. Surplus protein is deaminated, producing nitrogen that must be eliminated via the kidneys. This leads to:
-Increased water consumption and urine output
-More ammonia in stalls, contributing to respiratory irritation
-Potential digestive upset (Elisha Edwards)
2. Weight Gain & Energy Excess
Because alfalfa is more energy-dense than grass hay, horses who donโt have high caloric demands (e.g., easy keepers, idle horses) can gain excess weight, which may increase risk for laminitis and metabolic issues.
Equine Programs
3. Mineral Imbalances & Orthopedic Concerns
Long-term feeding of high-calcium alfalfa can interfere with normal bone development in growing horses and potentially contribute to developmental orthopedic issues.
horseracingsense.com
4. Heat & Hydration Effects
Protein metabolism generates more metabolic heat than fats or carbohydrates, which can be problematic in hot weather or for endurance horses. Excessive water turnover may also increase risk for dehydration if not managed carefully.
Equine Programs
5. Enteroliths & Stone Formation
Feeding alfalfa can be associated with increased risk of intestinal stones (enteroliths) or urinary stones, especially with limited movement and confinement.
Horse Health and Nutrition
6. Metabolic & Sensitivity Issues
Some horses prone to insulin resistance, equine metabolic syndrome (EMS), or laminitis may respond poorly to even low-sugar alfalfa, due to amino acids influencing insulin responses. Horse Health and Nutrition
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Sainfoin & Other Legumes
Like alfalfa, sainfoin (Onobrychis viciifolia) is a legume and shares many of the nutrient traits โ including higher protein and mineral content โ though it also contains condensed tannins that may help gut health and parasite control in some cases. Legumes, in general, tend to be richer than grasses and require similar consideration for balance and suitability based on the horseโs metabolic and physiological status.
