The term "mistress" historically refers to a woman who has control or dominance over something or someone. In an animal context, it could metaphorically describe a person's mastery or deep understanding of animal behavior, training, or a special bond with a particular animal.
The phrase you provided appears to be a collection of keywords. The interpretation depends heavily on the context in which these words are meant to be used. animal mistress beast dog
For the beast dog, the benefits include: The term "mistress" historically refers to a woman