Years ago, I took one or two online courses through Guelph for some additional learning and something to do. I don’t recall if I took Equine Nutrition, but I did take Equine Behaviour. The course and instructors may have changed now, but I recall rapidly losing interest in it at the time. I found the topics discussed were often incredibly specific and didn’t relate to horses as a whole. There also seemed to be a big focus on clicker training.
Some books I have on hand are:
Equine Nutrition and Feeding (4th edition) by David Frape
Nutrient Requirements of Horses (6th edition) from the National Research Council
Equine Behavior by Paul McGreevy
The Horse Conformation Handbook by Heather Smith Thomas
Equine Science (4th edition) by Rick Parker
The Comprehensive Guide to Equine Veterinary Medicine by Barb Crabbe, DVM
My experience may very well not be indicative of other people’s experience with online courses. I’ve found that between the books available for purchase and the resources online, I have access to quite a wealth of info. However, if you’re interested in pursuing some online learning, go for it. Maybe you could inquire with some of these web based schools if they could forward you the syllabus for this past year’s Equine Nutrition course to see if it fits your fancy?