Which breed is recognized for being commonly used in market hog competitions due to its leanness and yield?

The breed commonly recognized for its leanness and yield in market hog competitions is the Hampshire. This breed is notable for its muscular build and ability to produce lean meat, which makes it a popular choice among those looking to compete in market shows. Hampshires typically offer a good balance between muscle and fat, leading to desirable carcass traits that judges favor in competitions.

Other breeds like Yorkshire and Duroc are also used in competitions, but they tend to excel in other traits, such as maternal characteristics or meat quality, rather than specifically leanness and yield as prioritized in market hog competitions. The Suffolk breed, primarily known for its sheep, does not fit within the context of hog competitions. Therefore, the Hampshire stands out as the breed most often associated with market success due to its distinctive lean attributes.