I've looked into this myself and learned a LOT, and it's still my other option if I decide not to go with my current plan. There are a few helpful things you can find on Google by searching "Equine Nutrition jobs/salary/schools" etc.
Please take this with a grain of salt, as I am not an expert, I just remember what all I read and heard on the subject.
The most probable job you'll get with a degree in equine nutrition will be either in private research (for a university or an equine pharmaceutical company) or in actually analyzing the components and results of feeds for brand-name companies, such as Purina Mills, Nutrena, etc. "Working with test horses" would be appropriate, although I would like to point out that it's not as unsafe or risky as working with new human medications on test animals. You will oversee the diet plans of horses on both an individual and test-group basis, according to the current fitness and workload of the animal you're working with.
In research, you'll be more likely to develop new ideas and products for horses as a whole; in other words, rather than working with a specific company on a specific goal for a specific need, (i.e. - better feeds for high-end competition horses,) you'll be working to solve problems that affect horses and owners more universally. You might incorporate a new ingredient into feeds that can put weight on more quickly and safely, or you could develop a supplement that helps calm mares or stallions.
I'd say work at a pharmaceutical / equine supplement company would pay the most, and you would most likely be doing little hands-on work with horses -- more or less, you'll be dealing with statistics and the, uh, "results" of their digestive system, aka poo. You'll need to be okay with handling the waste of these animals, as it will tell you a lot about what's going on inside of the horses' bodies.
As unappealing as that might sound, it actually seems to be a very interesting career choice, and as far as I've read and heard, it's got a fair amount of job options, especially for an "equine job," if you know what I'm trying to say.
Let's talk education.
To work conducting research at a university, it's almost (if not strictly) always required that you have a doctorate in your field of study. I think with a master's, you could assist in research and work at certain positions in feed and horse health/dietary companies, and maybe in lower-level or assistant positions in private pharmaceutical research. About working in research;
I'm going to be working in a research field myself, and in this career area, you're going to want to be able to write very, very well on a technical and "slightly" creative level. Research is usually conducted using private funding, and to earn the money you need to fund your research, you have to be able to write for grants. Employers looking for prospective workers absolutely crave a candidate who is not only educated in their field of study, but who are also perfectly capable of earning the money needed to fund the projects they'll be work on.
I'm unsure of what sort of job you could get with a bachelor's, unless you worked for a very serious (and very wealthy) high-end competition company or farm. As far as I know, those sorts of jobs are few and far between, but very rewarding, as you'll be working with some of the top competition horses in the country to make them feel and perform at their best. I'm sure that race horse trainers consult nutritionists on the dietary needs of their athletes, though on how personal a level, I'm unsure. I believe pay in this sort of job would be quite variable; it could be minimum wage, or it could be incredibly rewarding, and you could be offered amenities (such as a barn apartment,) or you could need to have your own quarters and means of transportation, etc. It all depends on who you work with.
Also, if I remember correctly, if you plan on getting a higher degree, you can try for a bachelor's in equine nutrition; but honestly, I think it's a hard degree to find, especially on that level, and from what I remember reading, most people pursuing a graduate-level degree in this field major in either equine science or general animal science before going on to graduate studies. These degrees are much more widely available; I'm pretty sure most schools with an agricultural department will offer a degree at least similar to those.
It also wouldn't hurt to get a good background in sciences like biology, chemistry, or even biochemistry, which deals with the biological aspects and processes of living creatures on a more "chemical" level. Digestion/metabolism, hormones and the endocrine system, (all of which you'll need at least in your graduate studies,) are all taught in these courses, as well as quite a few other things. While the animal science programs will touch on this on a more practical level, it's always a good thing to have a strong understanding of the scientific processes on a molecular and cellular level.
I'm not sure of all the schools offering programs and degrees, but I know UK (University of Kentucky) offers a program, but it is
a graduate program. The site has changed since I read up on the program extensively, but I've not read anything saying they no longer offer the program. I believe it was a bit selective, but this is somewhat of a narrow field, and education in this area isn't as easily available as would a degree in, say, physical therapy or another human science would be.
Their prerequisites included a degree in animal science or equine science, I believe. I'm just going to give you the link. Here is their equine page.
If I'm not mistaken, there was also a school in Texas that offered it as well. It might have been Texas A&M, but again, I'm not sure. I never really looked into much else than UK, since it's closer to home, and apparently their agricultural department is respectable. (I also had family that went there and live nearby.)
But yes, that's what I know... sorry if I haven't helped much, but I encourage you to do what was suggested above and write more knowledgeable people about it, such as Purina Mills or even an adviser at the University of Kentucky or another university that offers degrees in this area. If you do write people, there is a chance of learning of a program that would help you financially or score you a job after graduation; some programs help you with your tuition and college costs if you promise to work with them for a certain amount of time after graduation, although I'm not sure if this applies in equine nutrition.
Allow me to think hypothetically for a moment. Even if you're unable get a job in research or in a company, (since the economy has gone to hell, of course,) or if you need a change of scenery after years of working in one of those areas, think of this; you have a degree that opens doors to higher positions in places like equestrian center management, especially
if you majored in an equine science area that included equine management aspects.
It's always important consider all your options and have a backup plan if things do fall through. It can seem daunting, but in the end, it's truly worth it.
Also, I read this somewhere as well, and I want to relay this information to you. I'm paraphrasing, as I cannot remember the exact wording. . .
A career as an equine nutritionist is on the same level as being a large animal vet, education-wise. It's just a much more narrow field with even less prospective students.
Statistics have shown that there will be a good deal of need of large animal vets and highly-educated people in the field of large animal health over the next twenty years or so, with fewer and fewer people interested or, (more likely in this economy,) able to go through the schooling required to earn the more necessary degrees. The job outlook is strong for large animal vets and large animal health practitioners.
Nutrition is certainly in the health and medicinal field of the equine industry, and I'd imagine this would apply to the above statement.
. . . And I'm done paraphrasing.
Anyway, if you're interested in this sort of job, I strongly encourage you to look further into the schooling and the career as a whole. It can be time-consuming and even frustrating; I know how that is and how it feels, but if it's something you're truly interested in pursuing, then by all means, go for it! If it's not what you're interested in, that's fine too; just keep looking around, and in time you'll find a career that fits you and your goals.
Sorry for the ridiculously lengthy post, but I hope I've helped at least a little. Good luck!