The Belgian Blue is a unique cattle breed that was developed quite accidentally in the late 1800s. An chance mutation lead the cattle to develop 'double muscling,' which occurs when the body does not produce sufficient myostatin to regulate the growth of muscles.
These body-builder animals typically have 40% more muscle mass than the typical cow or bull. Double muscling is an extremely rare occurrence. Outside of carefully selected breeds like the Belgian Blue or the Texel sheep, it has occurred only a handful of other times in animals like dogs and humans.
Animal rights activists contend that the breed is inherently cruel. Calves are usually delivered by cesarean section, as they are too large to be born naturally. Due to its massive size, the breed suffers from heart and joint problems, and can have difficulty even moving around.
Both Denmark and Sweden have both attempted to ban Belgian Blues on grounds of cruelty. From turkeys that can only reproduce via artificial insemination and bulldogs that must be born by c-section, we've created a catalogue of organisms that could never survive outside of the human environment. Think of it as triumph of co-dependence.