A very well-known advocate of the small, grass-based farm who will go unnamed, but we owe him a lot, tells us he is line-breeding his large flock of multi-breed chickens for a landrace that will thrive on his land, under his methods. Bravo! Where a large number of livestock are kept, the selection for breeding of individuals of whatever genotypes which perform well in that place seems the way to go.
For us tiny-farm people, where a very limited number of individuals can be used in any breeding program, maybe it helps to start with a narrower range of genotypes already selected to perform well under conditions similar to our own. Like, one breed.
Pursuant of that object: Today we culled the Pekins and Cayuga ducks from our flock, which is now pure Silver Appleyard. Likewise, we are limiting our flock to only Buckeye chickens for breeding purposes, only Pilgrim geese ditto.
And the farm cats? With the death of Samson, our aged and raggedy black tom, we are now the only farm we know of to specialize in felinus domesticus var. Holsteinus.