What are the principles for selecting breeding pairs in dogs? A detailed explanation of the precautions

Selecting breeding pairs in dogs means choosing suitable male and female dogs to mate, that is, how to choose suitable mates for male and female dogs. The principles are as follows:

(1) Choose male and female dogs that share common strengths to mate, so that their strengths are maintained, consolidated and developed in the offspring.

(2) Male and female dogs that share common faults must not be mated; if they are mated, the faults of both will become more firmly established.

(3) When good breeding dogs are in short supply, a dog with a certain strength may be mated with another dog that has the corresponding fault, using the strength to overcome the fault. Note, however, that a convex back cannot be used to correct a concave back, and an "X" leg stance cannot be used to correct an "O" leg stance.

(4) As for the age of the pairing, the ideal is prime age with prime age, or an older female with a prime-age male; pairing old with old should be avoided as far as possible. Dogs over 5 years of age that have never been bred before (virgin dogs) are not suitable for breeding.

(5) When selecting a pair, note that the body sizes of the male and female should be appropriate so as to avoid injury. Except for special needs, inbreeding (within three generations) is strictly prohibited.