I am currently doing a study (as part of my course) on quarantine regulations and I was trying to find out information on the rules regarding for example buying a stud dog from abroad.  Is there any special rules on this topic.  Thanks in advance

Basically you can't get a dog into the UK under 10 months old on the Pet Passport system, and probably 8 months using quarantine, or the same using Traded Cats and Dogs rules that mean the animal has to have been kept isolated by the breeder in the european country for 6 months since birth, but that system would not be in the best interests of the animal at all with the Pet travel scheme now available.

Your best place of reference will be DEFFRa who will have all the regulations for all 3 import methods.

There are no regulations on bringing a stud dog in.  Quarantine now is really only viable if there's no way that the breeder of the dogs will keep them for the 8/9 months needed for the scheme.