Sponenberg doesn't appear to have a complete understanding of population genetics, genetic drift, trait selection, and pedigree errors.
I'm surprised by some of the serious flaws in his presentation in the section on Dexters. I'm also surprised by his seeming lack of understanding of genetic drift and trait selection. Without a focus on trait selection and an understanding of genetic drift, you can't preserve anything at all.
Mutations and genetic drift, and selection decisions are very powerful. A focus on pedigrees won't help with preservation at all... In fact, it can hurt preservation by tricking breeders into preserving an animal that has drifted away from the target of preservation.
I'd love to have an exchange with Sponenberg to help him understand it better.