By Helen Briggs
BBC News science reporter
The blood would be used for emergency trauma cases and during complex operations such as open heart surgery.
Specialist centres are now offering pet owners hi-tech treatments pioneered in human medicine, including hip replacements and radiotherapy.
But they come at a cost - with some owners spending thousands of pounds to save a much-loved family pet.
Dr Jerry Davies, Council Member of the Royal College of Veterinary Surgeons, and founder of the largest specialist veterinary referral practice in Europe, said that pets were worth more than their commercial value.
"Animals do have a huge benefit to the human population so we should be striving to help the animal for the animal's sake and also for the welfare of the human attached to them," he said.
Mr Dan Brockman, an expert in cardiothoracic surgery at the Royal Veterinary College, London, said he was now carrying out several open heart surgery procedures a year.
Other surgical procedures for dogs and occasionally cats - including heart valve replacement, heart valve repair, cancer operations, and knee-, hip- and elbow-replacements - are becoming routine.
The cost of between £3,000 and £10,000 is met by pet insurance policies or by the individual.
"Pets should be considered a luxury item," said Mr Brockman. "What we do is not for every owner. The important thing is that part of responsible pet ownership is to at least give thought to what you might do if your animal became ill."
Many such operations relied on the "benevolence" of owners of large dogs who were prepared to let their pets donate blood, he said.
"One of the things that has held back critical care in the UK has been an unwillingness to develop blood banking in the UK," Mr Brockman told reporters at the Science Media Centre, London.
"It's not possible to have a well functioning trauma centre without having blood product support as in human trauma medicine."
Mr Brockman said it should be possible to create a central blood banking facility or several regional centres so that blood could be extracted, stored and moved to where it was needed.
"I think it is only a matter of time; I really hope one will be set up." he added. "Personally, I would like to see someone fund a non-commercial venture - that would be much better but it would cost money."
Large dogs of 25kg and above with a calm disposition are suitable as blood donors. The dog is made to lie down, has a needle placed in a vein in its neck, and 400ml of blood is collected over the course of 10-15 minutes. A typical heart operation would use three to four blood transfusions of this quantity.
Dr Jerry Davies said about 100-150 dog owners, and about 100 vets, had signed up to a preliminary blood donor scheme launched on the internet. Critics of the idea have raised commercial, legislative and ethical objections.