Canine Blood Donor Clinic.

[Catherine]

The Canadian Animal Blood Bank organizes Blood Donor Clinics for dogs regularly. A healthy dog over 55 pounds can give blood every 3 months. 
The dog must stay healthy and be comfortable with the process. This allows veterinary hospitals to have blood on hand for emergencies.

https://www.ctvnews.ca/atlantic/nova-sco...or-clinic/

The process doesn't take long and many dogs  are comfortable with donating. This is a life giving gift, the same as human blood donations. 
It is beautiful that people and their dogs are willing to help other dogs. The important thing is that the dogs and the people freely choose to do this.