Question
What are the nutritional differences between legume hay (alfalfa) and grass hay?
Answer
There are several nutritional differences between legume hay and grass hay. In the United States, legume hays typically include alfalfa and clover. Grass hays include many varieties of grasses and can include the grain (oat) hays. One of the biggest differences between legume and grass hay is protein content. On average, legume hays contain much higher levels of protein. It is not uncommon for legume hays to contain in excess of 15% protein while grass hays typically will contain 10% protein or less. The extra protein contained in legume hays is not dangerous for horses since they break down the extra protein and utilize it for energy. The downside of this extra protein is the nitrogen must be eliminated from the body. The horse will drink more water and urinate more frequently.
The energy content is also different between legume and grass hay. Legume hays contain more calories per pound than grass hay. This higher calorie load in the legume hays translates into fewer pounds of hay necessary to maintain body weight. This is not particularly good news for those horses that already have trouble keeping their weight down. The reason for the higher calorie content in legume hay is a lower fiber content. The higher fiber level in grass hay allows horses to eat more feed without putting on weight. This is the reason that most nutritionists who want to reduce the calorie intake of horses advise that grass hay be fed.
The other major difference between legume and grass hay is the mineral profile. The calcium content of legume hays is typically very high in relation to the amount of calcium in grass hays. The phosphorus content is not that different between grass and legume hays. Since calcium is higher in legume hays and phosphorus is nearly the same, the ratio of calcium to phosphorus in legume hay is quite high. This ratio is important for proper bone growth. Hay containing an excess of calcium without adequate phosphorus can lead to bone anomalies.
