You can feed baleage to horses, however, there are some precautions you need to take. Horses are very susceptible to botulism, which is linked to baleage and is often fatal. Horse owners who are feeding baleage should consider vaccinating their horses with at least two initial immunizations against this disease and then continue with yearly boosters. However, the vaccine is rather crude and causes considerable vaccination reactions in some horses so it is not a decision to make lightly. As baleage feeding is uncommon, most veterinarians are unlikely to have the vaccine in stock so they will most likely need time to order it.
If hay is short, consider feeding alfalfa cubes, beet pulp or increasing the horse's grain. However, remember that horses need their diet to consist of at least 2/3 forages in some form or another.
By Julia H. Wilson, DVM