I think line breeding is when you have an excellent male and cross him to his daughter then grand daughter then great grand daughter. So if you look at the pedigree it goes in a line. Not stating facts just what I have heard. Supposed to be some good information on the texas A&M website. You can use a mother and son but think it could produce more birth defects that way.
Dogs pulls from anywhere in the ancestry so formulas like this are "relative" to the dogs used in the breeding. In others words this does not apply to every dog or breeding.
