The best bulls are used to adjust the genetics for portions of the entire herd. Some bulls tend to have bad feet (these you don’t keep), are predisposed to genetic defects (double muscling), cancer, slow weight gain, large calves, etc. you don’t want this.
The unicorn bull throws a small calf with fast weight gain and has no genetic defects in his history that would lead to poor performance on his offspring. If you breed 50 cows to a given bull, all 50 calves could wind up with these genetic issues.
This guy has genetics going back to a bull named Roughneck (he was a famous Shorthorn bull whose semen was used widely for desirable traits). The dominant desirable traits are calving ease (CED), low birth weight (bw), weaning weight (ww), yearling weight (yw)… the carcass traits are carcass weight (cw), ribeye area (rea) and this is actually measured on a live bull using ultrasound.
Here is his paperwork:
