"make a small profit of £30 per dog whereas other breeders in the area sell "purposely bred" beagles for as much as £200, leaving little room to wonder why labs choose them."

While this isn't intended to represent support for the use of animals in experimentation, those of you who are opposed should know at least the basics. Pretending that the scientists have no interest in doing science, "just want to torture dogs", results in the wort of nonsense just spouted. So I'll try to explain WHY specially bred dogs and beagles in particular.

Of course it depends upon the particular experiment how much this matters, but in general the animals used should be identical as possible. So if dogs are to be the animal, then what they want are beagles, which are a smallish breed, have a very small genetic base, and at the same time are plentiful. What I mean by "small genetic base" is that any two beagles are likely to have more genes in common than would be true for most breeds. Increasing this effect are that these suppliers of "purposely bred beagles" are supplying batches even more closely related, can supply say 100 beagles all descended form perhaps just four ancestor beagles.

In general dog breeds are created by inbreeding or at least breeding within a population small compared to that of the species. For most breeds that means many dogs with geentic defects. By some quirk the breed "beagle" started out with a smaller percentage of "bad genes" and so are OK even though lacking in genetic diversity.