The phrase "predominant breed" refers to a type of animal species that is most commonly found or prevalent in a specific area or group. Full definition
And the bulldog became top dog in Los Angeles (despite other surveys that say Chihuahuas are the most predominant breed there). (ohmidog.com)
Compared with controls, biting dogs were more likely to be German Shepherd or Chow Chow predominant breeds, male, residing in a house with ≥ 1 children, and chained while in the yard (celiasue.com)
They do ask questions like what predominant breed you think your pet is, but we left it blank. (amazon.com)