Vampires have invented a safe, easy means of removing blood from animals without constantly jabbing them with needles and alarming them. A simple band, with a specially made IV tube in it that opens and closes to prevent the creature from bleeding to death, and antimicrobial enchantments to prevent infection. But magic can't keep the collar in place, only good sense can. What animals would be the best candidates for this, and what placement of this band is best? Note: It is preferred that the animals selected are common domestic animals.
The only real issue is you want placid animals, like common livestock and not pets. After that it is entirely up to you, based on the vampires food preferences the only thing that will really change from animal to animal is volume of blood you can remove. We have had ways of immobilizing animals for centuries, and attaching things to them for decades, once infection is no longer an issue the sky is the limit. We have cows that you can open up valve the side of and stick your hand in their stomach, keeping a collar in place is not an problem. We already have ways of harvesting animal blood for hormones and antigens anyway. A placement on the body or neck will work fine.
Here is a medical breakdown of methods and animal selection criteria, just to warn you it is automatic download.
Dogs. It's a bonus because they're very common, and a vampire can additionally hide his identity as well. Sucking the blood out needs private place though.
The collar can be disguised as second "collar" just beneath the real collar. Putting it as the real collar won't work, obviously.