Ask the expert: Can I feed soybean hay to my horses?
Question: I'm having a hard time finding hay. A neighbor is planning to bale their soybeans due to drought conditions. Can I feed that to my horses?
Response: Soy is a common ingredient in horse rations and is a highly digestible source of protein and fat. Soy (e.g., meal and hulls) is usually included in horse concentrates or grains, but is rarely fed as forage.
While research conducted in the 1920s suggests soybean hay can successfully be fed to draft horses, limited research has been conducted since. However, research with other livestock species suggests that soybean hay can be unpalatable and should only be included in limited amounts in the diet.
Chopping and ensiling soybean hay can improve palatability, but these options are rarely practical for horse owners. Additionally, soybean hay containing seeds (e.g., the actual soybean) should not be fed. Unprocessed soybeans contain a trypsin inhibitor. Trypsin is an enzyme involved in the digestion of many proteins, but once soybeans are processed (e.g. roasted), the inhibitor is denatured.
Therefore, soybean hay should be fed to horses with caution and in limited amounts. Horses should be transitioned slowly to soybean forage and it should be free of mold, weeds, dust, and harvest restrictions for herbicides and other pesticides must be observed.
Soybean hay should also be tested for nitrate accumulation prior to feeding.