I’ve been able to scare off a few steers and a few bulls by putting my arms in the air and walking towards them slowly.
The time it didn’t work however, the thing ran into the 4 strand barbed wire fence to the point of snapping off the T-posts…….when it finally stretched as far as it would go, it threw the bull back into the pasture. Not cool…..I was scared. I don’t put my arms in the air anymore, I just avoid the pasture. 
My dad, a lifelong dairy farmer, swears that they can’t run fast downhill because it hurts their junk. I’m not going to be the first (and last) one however to test his theory. 
Joel