The Armour Beef Cattle Improvement program lasted from 1960 to 1967. At the end of the testing period the Diamond C Ranch was one of the most recognized ranches in the world.
Eight hundred fifty (850) beef cows were being AI (artificial insemination) bred on the 14,000 acre Diamond C when semen from many of the European breeds became available in the U.S. Although John B, IV was still in college, he was making most of the management decisions concerning genetics and performance testing on the ranch cow herd. He saw a bright future for these new breeds, especially Simmental.
The Diamond C became one of the first U.S. ranches to AI breed Simmental, Limousin, Chianina, Maine Anjou and several other European breeds. All the resulting 1/2 blood females, with the exception of the top end of the Simmental, were sold. The Simmentals heifers were kept for replacements in the Diamond C Ranch herd.