My name is ***** ***** I’ve been involved professionally with dogs in the health and behavioral fields for over 18 years. It will be my pleasure to work with you today.
Line breeding is basically inbreeding which is breeding two dogs closely related. If the grandfather in question was an excellent example of the breed in all ways such as conformation, personality and health wise, then the shared grandfather might actually be a desirable thing. Many breeders will breed back to a grandfather or a dog with a shared ancestor to help fix that dog's traints in the resulting pups and bloodlines. With just that one shared grandparent, it really shouldn't be much of an issue as long as he and his offspring haven't had genetic issues such as joint, heart or eye issues.
While inbreeding can fix desired traits into a bloodline, if the common ancestor had genetic issues, the genes for those undesired issues might be doubled up but like I mentioned, it usually isn't much of a problem with just one shared grandparent. If any of the other dogs in a the pedigree were doubled up, then I would be more concerned. So do your research and check for health issues in the shared grandparent and his offspring as that will give you the most information on potentially genetic issues being passed down to pups.
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