Wild cattle were thick in the Texas brush and after the Civil War it became common practice to round them up and herd them north and east to market. At the same time, ranches were developing with other breeds of cattle in Texas, Colorado, Kansas, Wyoming, and Montana. These ranchers didn't want the Texas longhorns using the same forage and crops as their American cattle used. The Texas longhorns also carried the disease-bearing tick that caused tick fever; the Texas longhorns were immunne but not so the American cattle. The ranchers also believed that the longhorns were a danger to other livestock and to their crops.
16 common cattle breeds | Living the Country Life
Over the centuries, Brahmans have developed resistance to pests, ..
Breeds of Livestock - Veterinary Medicine