It is strongly suggested that your keep broccoli away from your horse, along with cabbage, cauliflower and a list of others things. These foods may cause gas, which in turn may cause gas colic, which is excessive gas in the horse’s abdominal tract. Although there is a good chance that gas colic will be noticed and successfully treated, it can be very dangerous for your animal.
And even though many horse enjoy the taste of broccoli and will eat any that they are offered, it hardly seems worth taking the chance. Some may believe that it is alright to feed a horse small amounts of broccoli, but in doing so you are taking a serious risk.