I grew up on a farm in western Kansas, we had cattle as did most everyone else in the area.
Cattle can be conditioned to come to your location by certain yells, whistles, vehicles horns, or whatever. They will ignore the typical vehicle horn unless conditioned to it, i.e. such as blowing it every time you feed them.
However, a bull horn when sounded will bring any herd toward you without being conditioned to the particular horn. I don't know the reason they respond to the particular sound of a bull horn, but cattle will come on the run toward where it is being sounded from.
No bull, just fact.
