Many pets aren’t as fortunate as Phoenix. Not every vet clinic carries blood products. Even those that do are perpetually at risk of running out because blood is composed of living cells that age and die. A unit of canine or feline blood has a shelf-life of about a month, and after that they expire and are discarded. While you can freeze plasma, it is difficult to cryopreserve red blood cells, and that approach is not widely used.