The most popular supplements that are added to the diet is something that will help add bloom and keep animals "fresh" looking. In Oklahoma and Texas, the most common types of show feeds are: Moormans, ShowRite, Sunglo, Suthers, and Acco. (Ranked in decreasing order).
Calf Manna is really popular among all types of livestock. Horses, calves, and hogs are some really good speicies to focus on to market this product. Since sheep have a low tolerance for cooper, enhence they can die from very small toxic amounts, it is hard to pin point something that would help them.
Keeping electrolytes and milk replacer on hand will also be a big seller.