Thanks for the replies. I am not ignorant to the controversy surrounding the Biewer breed, but I personally believe that they are a different, separate breed despite having originated in Yorkies. Darling von Friedheck was a purebred Yorkie and this is where the foundation of our line comes from.
If you look at how new breeds have emerged in the past, you'll see that mutations like this often leads to new breeds. For example, all spaniels come from the springer spaniel. The cocker spaniel was once a mutation and someone decided that they liked the attributes so much that they wanted to create a bloodline from it.
This is what Mr and Mrs Biewer did and I like the results so much that I got involved in the breed. I had Yorkies first but they aren't breeding quality.
The Biewer bloodline breeds tricolour babies of high quality consistently and this is why I wouldn't outcross with a Yorkie - it makes your line more inconsistent and that's the opposite of what a breeder wants.
__________________ Cash & Orio  RIP Beautiful Joni |