There are many ways of collecting the blood. However, the simplest way would be via retro-orbital bleed. I have attached a methods paper outlining the procedure.
You will need permission from your animal use committee anyway, so it is best to contact them first about which methods are permissible at your institution and where to get any training necessary.
Hi, there is a paper "A good practice guide to the administration of substances and removal of blood, including routes and volumes", which helped me a lot in my time. The removal routes are explained in detail including the allowed upper limits of blood per time frame. Good luck!
Article A good practice guide to the administration of substances an...