Horses must be tied high because of their high set necks and powerful hindquarters which they can get well up under themselves to use their full force, which is a recipe for disaster if they set back. Cattle on the other hand, are not likely to break their necks when tied low because they have a lower set neck, are typically lower fronted, and do not have the collection and setting back power of a horse. This really isn't about physiological differences so much as it is about behavior. Cattle like to lay down when they have nothing else to do, so a calf left standing tied will be more comfortable if it is tied low where it can lay down. On top of that, I really don't think this calf isn't gentle enough just yet to benefit from being tied high. If she sulls up and throws herself down she could be left hanging where she can't get up, and that's scary for her and dangerous for who ever has to untie or cut the rope to get her down. If she is tied low and throws herself down she can easily get back up on her own and it is a more positive learning experience in that she can figure out on her own that halter breaking isn't the end of the world and no one is trying to kill her. Frankly, I believe the only reason to ever tie cattle high is to teach show calves to hold their heads up and that is only for short periods of time. I am not here to argue. These are just observations I have made halter breaking countless show calves and horses.