If an animal requires blood during surgery where does the blood come from? Do Veterinary Surgeries store replacement blood for species they frequently operate on and if so do animals such as cats and dogs have different blood types as humans do?
Large veterinary practices sometimes keep blood donors on site and bleed them as needed. For smaller practices like mine, commercial blood banks exist and I can purchase and overnight blood products as needed. Oftentimes, the choice is made (due to economics) to go without.
Here is a page concerning dog and cat blood types and blood banking.
http://www.vet.utk.edu/bloodbank/
From memory, I may have to research later:
Veterinary clinics usually use the pets of the people that work there as donors, although some larger hospitals like those associated with vet schools have organized donor lists, and every now and then ask people to use their pets as donors.
I think both dogs and cats have different blood types, just like humans. The difference is that in one case (I think dogs) mixing blood types won’t cause a negative reaction (at least the first time), and in the second case, even though mixing blood types may cause a reaction, most of the animals (I think cats) are of one blood type, so your chances of having a negative reaction are diminished. And since transfusions are usually done in life or death situation, the gamble is worth it.
If you check the archives on this site, you can sometimes find an article that addresses such a question. Like this one: http://www.straightdope.com/mailbag/manimalblood.html
My vet used his own pussycat as a donor. This cat was almost 30 lbs, and not just fat - also tall and long and muscular with a huge head. Nice cat, too. He died recently at a fairly advanced age. Vet’s still alive and kicking, tho.