Yuki is a huge triple hybrid gray wolf who is almost 90% wolf, with 9% Siberian Husky and the rest is German shepherd. It looks like it is an example of hybrid vigour. Sometimes when different species or breeds are crossed the resultant offspring are larger and stronger. It is the injection of fresh genes which does this. Conversely when there is inbreeding the opposite happens, the offspring have compromised immune systems and they can be small and lack robustness.
Two useful tags. Click either to see the articles: Speciesism - 'them and us' | Cruelty - always shameful