I am submitting 5 eLORs with my VMCAS application this cycle. For those schools that choose to read only 3, I have listed the top 3, in order of importance, in my explanation statement.
My 3 eLORs were written by individuals (one DVM, one PhD, and one MD) who actually supervised my work. The other two (one DVM, one PhD) are professional colleagues with whom I've worked closely throughout my professional career, but who were not formal supervisors. The final two letters are important, and add a unique dimension to my candidacy, but should be considered 'lower priority' than the top 3, because the authors were not direct supervisors.
Go with your gut as to whom you think would argue the best case for your admission to veterinary school. If it's more than 3, submit them. Keep in mind the advice that other folks have offered- some schools may choose to read only three. Find a way to impart to the school your selection as to which three are the most important. Lynn Maki at the University of Wisconsin suggested that I email her directly to inform the admissions committee as to which 3 LORs I considered to be the most important. She was clear in telling me that Wisconsin's admission committee may, in fact, decide to read all 5. In the case that the members did not, however, she wanted to give me the benefit of the doubt in having input in to the selection process.
Only you can decide which individuals from your past and present will best represent you. Go with your gut.