The objective in pure-bred dog breeding should be preservation of the breed. The Afghan Hound Club of America, Inc. has in their Constitution and By-Laws a clause that states: “The objects of the Club shall be: (a) to preserve and protect the breeding of pure-bred Afghan Hounds and to do all possible to bring their natural qualities to perfection; …” Many other parent clubs have a similar clause in their Constitution and By-Laws.
Many breeders believe their task is improvement of the breed. Improve means to bring to a better quality, it does not mean to change. As long as the improvement is to bring to a better quality while maintaining the basic original purpose of the breed that is acceptable. Eliminating cow hocks in a breed that has a sustained trot as part of its basic original purpose is proper. Producing All American Show Dog movement, instead of maintaining breed specific movement, will lead to the loss of the breed. Many breed clubs have "codes" that call for improvement - but the improvement intended must be within the context of the Standard and the basic original function of the breed (i.e.: breed preservation). If the "improvement" goes beyond those bounds you now have a new breed.