Not only do they need to have the same amino acids, but they should be present in the same relative percentages. Soybean oil meal is especially high in lysine, which is commonly low in most grains. Soybean oil meal is also usually the cheapest source of protein available for horse feeds. Soybeans should not be fed to horses in their raw form. In the raw form they contain an inhibitor of protein digestion in the horse.
Raw soybeans are especially detrimental in foal rations.
Linseed Oil Meal Linseed oil meal used to be in great demand for inclusion in feed rations for horses. This meal is high in sulfur-containing amino acids, which were thought to aid the quality of the hair coat. Actually, the quality of the haircoat came more from the oil in the meal. However, modern processing removes most of the oil, thereby decreasing its value for horse feeding. Linseed has been recommended in rations of horses that suffer from tying-up syndrome, because it is a good source of selenium, which helps maintain normal muscle function.