Hi Miajasmin,
I'm currently a vet student at the univeristy of nottingham and did the EPQ during my A levels (coincidentally, you're also doing the exact same subjects I did), so might be able to offer some advice.
Any animal related topic is good, it doesn't have to specifically be about veterinary. You'll want a topic that has a lot of information available but also one that you can 'argue' with yourself about. My topic was "Is animal testing in human medicine needed?", which was great because there is a lot of evidence and arguments either way. Since you asked, I got an A* for my EPQ.
The topic of how vet science changed overtime is actually a really good idea, but you would need something to debate about within that topic. Maybe "Has veterinary science (the veterinary profession?) changed for better or worse in the past __ years?" or something like that. The veterinary profession has been undergoing massive changes in the past decade (gradual switch from privately owned to corporately owned vet practices, increased awareness of mental health and work/life balance, the public perception of vets changing, newer graduates demanding better hours and the rise of specific out-of-outs practices etc. to name a few) that this would be very relevant to current veterinary affairs. There is also a lot for you to talk about, as there are many good arguments for both 'better and worse'. It would probably be a very interesting EPQ.
If you have any questions or would like any advice please don't hesitate reply or pm me. I actually loved doing my own EPQ so would be happy to help!