You should always ensure that what you are feeding your horse is of good quality. The horses digestive system is quite sensitive and serious health problems can arise if you are to give them feeds contaminated with mould, dust, dirt or animal droppings. Molasses is sometimes used to encourage horses to eat foods that they are not happy with by disguising it's taste. This can be deadly to your horse if the feed is contaminated and then you cover that up with molasses and your horse ingests it. I always think if I wouldn't want to eat it then I cannot expect my horse to eat it.
Happy Riding Everyone!