Well-informed horse owners can usually provide a well-balanced diet for the equines in their care. The role of the equine nutritionist goes well beyond the basics, and includes going beyond a bachelor's degree in animal or equine science. A master's degree might find you employment, but consider attaining a doctorate to truly get ahead in the field.
Equine nutritionists work in academia, for feed companies, and do private consulting. Becoming an equine nutritionist is on a par scientifically and academically with becoming a veterinarian. There's a caveat -- veterinarians must be licensed, while that's not true of equine nutritionists. Technically, anyone can put out a shingle declaring herself an equine nutritionist in private practice, but for practical purposes no veterinarian would ever recommend an individual without proper educational qualifications. Equine nutritionists not only work closely with veterinarians, but are often recommended by them for clients in search of such expertise.