I agree for the need for boundaries, and I'm glad you're pushing for what you need.
But as someone who worked a salaried job in a completely different industry before this...it's really not unusual to be expected to pick up the phone if your job calls you on your day off to ask you a question or get your input on something.
It's the difference between a salaried employee and an hourly employee/shift worker. Patients (like projects) don't evaporate at the end of a day, and vets function in a leadership capacity in a clinic setting. I don't think it's crazy for co-workers to want to be able to contact you if they are in a crunch.
(Note - I'm not saying they should expect you to drop everything and come in to work, and I think having adequate time off/personal days/flexibility is SUPER important to employee happiness. But tbh I probably wouldn't hire someone who wanted to be totally inaccessible whenever they're off. Doesn't feel reasonable or team-oriented in a real world context.)
My mom's family has owned a business for 5 generations now, so I totally get that a lot of other professions do have an expectation of being accessible outside of work hours. My dad was salaried by his previous company as a manager of his store and was expected to answer his phone for 100% of his calls.
The family business is actually why I 1) never want to own my own clinic and just be a minion for the rest of my life and 2) never want to be contacted by work outside of work. My mom never got away from work, and neither did my dad, sister, or I (and dad was in a totally different industry). It definitely was a strain on my parents' relationship, and (in hindsight) a strain on my sister and I. And, because everyone on my mom's side was involved, the stores were talked about at Christmas, Easter, family dinners, etc etc etc. When my mom's lease was cancelled by the mall, she ultimately made the decision to not reopen at a different location (that was cheaper and in a better area) because the store took up her entire life. Even now, because my aunt and cousins are still involved in the business, my mom and I get dragged into things (conversations, advice, etc), and she and I have been out of the business as a whole for officially 5 years now. My sister would flat refuse to do anything work related to the stores. I don't regret growing up in the family business; it's why I wanted to become a vet in the first place. But the family business definitely taught me what I do and do not want going on in my life.
While I understand colleagues may want to contact me if say, I see a patient the day before and they come in on my day off. They may want to get my opinion or help on a case that they're having trouble with. There are definitely a ton of scenarios in which the clinic will want to get a hold of me. But it doesn't seem reasonable or team-orientated to me to have employees work when they aren't at work, hourly or salary. I strongly feel that someone's responsibility to work (as an employee, not an owner) ends the moment they walk out the door. My employer has no right to my time and energy that they aren't paying me for.
I very well may change my tune when job hunting; after all, a girl's got to pay her student loans and beggars can't be choosers. But the most important thing in the world to me is family and myself. And, not for nothing, the profession isn't going to change if people maintain the status quo.