The Royal School of Veterinary Studies small animals hospital in Edinburgh is putting out a call to attract new donor cats, as some of its regulars have grown too old to help.

While human blood, and even dog blood, can be stored for some time after donation, blood given by cats is best used within 24 hours, and is unusuable after a month.

When an emergency strikes, vets therefore need a list of pet owners they can phone to bring their cats in at short notice for fresh supplies.

The hospital's visiting clinical fellow, Nicki Reed, explains: "We basically collect the blood into a small version of the human blood donation bag. With dogs and with humans, the blood gets broken down into components such as plasma and red blood cells that get separated so they can be stored, but it's hard to do that with cats because the bags are much smaller." (Edinburgh News)

As well as helping cats on the operating table, the donations can be used to treat a variety of other problems, she explained: "It's used for cats that are anaemic, and occasionally we see cats who have had rat poison or have coagulating difficulties like haemophilia and cats that aren't producing enough blood cells."

New recruits are first tested to check for infections and to find out their blood type. The process then takes 15 to 30 minutes.

The vets are ideally looking for cats over 5kg with a placid temperament. Indoor cats are better donors because they are less likely to carry infections.

The hospital has a list of around 15 regulars, each popping in once or twice a year according to need. The most frequent donors are the staff's long-suffering pets, as they're easy to track down at short notice. Mrs Reed's own British short hairs, Will and Grace, have joined the list and Grace has already made her first donation.