strain, and a female of a tall, large-boned strain of white Plymouth Rocks. This first attempt at a meat crossbreed was introduced in the 1930s and became dominant in the 1960s. The original crossbreed was plagued by problems of low fertility, slow growth and disease susceptibility.

Modern broilers have become very different from the Cornish/Rock crossbreeds. As an example, Donald Shaver (originally a breeder of egg-production breeds) began gathering