Alfalfa hay, derived from the flowering legume Medicago sativa, is often considered for supplementing the diet of wild deer. Unlike grass hays such as timothy or orchard grass, alfalfa is a member of the pea family. The qualities that make alfalfa appealing to deer also pose significant health risks. This analysis explores the deer’s attraction to this high-nutrient forage and the physiological consequences of consuming it as baled hay.
Why Deer Are Drawn to Alfalfa Hay
Deer exhibit a strong preference for alfalfa, finding it highly palatable compared to many other available forages. This attraction is particularly noticeable when natural food sources are diminished or covered by snow. Alfalfa’s inherent tenderness and higher concentration of readily digestible nutrients make it an immediate choice for foraging deer.
Deer are classified as concentrate selectors, meaning they naturally seek out foods that offer the most nutrition for the least amount of effort. Alfalfa fits this foraging strategy well, especially when compared to the tough, woody browse that often comprises their winter diet. Large alfalfa fields often act as magnets for deer populations. However, the deer’s eagerness to consume the hay does not mean that it is a biologically appropriate or safe food source.
Nutritional Components of Alfalfa Hay
Alfalfa hay is known for its rich nutrient profile, containing high levels of crude protein, often ranging from 18% to 24% of its dry matter. This is significantly higher than the 6% to 10% protein found in the woody browse that makes up a wild deer’s winter diet.
The hay is also rich in readily digestible non-structural carbohydrates, such as sugars and starches, and has a lower overall fiber content compared to grass hay. This combination of high protein and rapid digestibility is disproportionate to the needs of wild deer. Alfalfa is also high in calcium, which can disrupt a wild deer’s balanced mineral intake.
The low neutral detergent fiber (NDF) content means alfalfa passes through the ruminant digestive system quickly. This encourages higher feed intake but is problematic for a deer’s specialized digestive process, which is adapted to process high-fiber, low-nutrient winter forage.
Digestive Dangers of Alfalfa for Deer
The greatest danger of feeding alfalfa hay to deer lies in the rapid change it imposes on their digestive system, specifically the four-chambered stomach known as the rumen. Deer rely on specialized microbes in the rumen to break down their food, and this microbial community is highly sensitive to sudden dietary shifts. When deer accustomed to a high-fiber diet suddenly consume a large quantity of high-protein, low-fiber alfalfa, the rumen’s environment is severely disrupted.
This rapid influx of highly fermentable carbohydrates and protein causes an overgrowth of certain bacteria that produce large amounts of lactic acid. This leads to a condition called rumen acidosis, or “grain overload,” where the pH level in the rumen drops drastically. The resulting acidity kills the beneficial microflora, causing the stomach to stop functioning and preventing the deer from digesting any food.
Another serious risk is bloat, common in ruminants consuming high-legume diets. Bloat occurs when the rapid fermentation of the hay produces gas trapped in a stable foam within the rumen, preventing the animal from releasing it through belching. The pressure from the trapped gas compresses the deer’s lungs, leading to respiratory distress and often death within hours. These conditions are particularly deadly in winter when the deer’s metabolism has slowed.
Responsible Wildlife Feeding and Forage Alternatives
Wildlife experts generally discourage the supplemental feeding of deer, as it can lead to habituation, unnatural congregation, and increased spread of diseases like Chronic Wasting Disease (CWD). The practice of concentrated feeding around hay bales also increases the risk of injury and predation. If feeding is considered absolutely necessary, such as during severe winter weather, it must be done with extreme caution and with species-appropriate feed.
Instead of baled alfalfa hay, safer alternatives exist that more closely align with a deer’s natural diet. Specialized commercial deer pellets formulated for winter use are a much better option, as they are balanced to provide slow-releasing energy and appropriate fiber. These pellets are designed to be introduced gradually to prevent the digestive shock caused by sudden dietary changes.
A more responsible approach involves managing the habitat to increase natural, year-round forage availability. This can include planting specific food plot mixes containing plants the deer can safely browse, such as certain varieties of clover or chicory. Providing access to natural woody browse, like the young shoots and twigs of maples and aspens, is the most biologically sound method for supporting deer populations during challenging winter months.