Legumes are much higher in protein and lower in starch than cereals. Of the plant feeds, they are the only ones with higher protein contents, although the protein quality is lower compared to animal feeds, with the exception of soy. Soy, peas, chickpeas and lentils are the most commonly used.
Soy has the highest protein quality of all and is therefore the most important vegetable protein source in feed, especially dried feed. Dried soybeans contain almost 35% protein. Soy protein concentrates (70% protein) or soy protein isolates (>85% protein) are usually used in dog food. Tofu is, in simple terms, a curd made from soybeans. Peas, beans and lentils contain approx. 25% protein and are a good alternative for allergy sufferers.
Legumes must never be fed raw. Some pulses contain an inhibitor that makes protein digestion more difficult. Others contain so-called antinutritive ingredients (e.g. tannins, lectins, glycosides, alkaloids) that are only harmless after cooking. Hard-to-digest carbohydrates (e.g. stachyose, raffinose) are also found in some varieties, which can lead to flatulence and soft faeces. This is probably the origin of the well-known saying about the bean and the clay.