Moobile infantry.
At first I thought that this was wrong, as we’ve been discussing bovine calvary.. Then I realized it’s udderly correct – draft animals taking soldiers to battle, but not used as mounts in combat.
What if they’re draft evaders?
I think the big issue you have with stampeding cattle at infantry is once it goes, you no longer have control. The enemy can see your herd coming at them and try to spook them to turn, possibly right back at you.
If you read accounts of elephants in warfare, while they were terrifying for the Romans and other Europeans to see, they weren’t exactly what you would call reliable.
Speed, manuevability and most of all control… that’s what made the horse the animal mount of warfare.
I can’t bullieve you made such a pun.
OK, so obviously a stampede would mess up a front line. The problem is the cows will stampede away from the scary-shooty people. But, what if a few cowboys could guide the stampede the right way? Maybe with like really hot pokers or something.
Cows with guns. The idea is not new.
I suppose you could use cows as a shock attack by getting them to stampede at the other guys. Beyond the hassle of traveling with a large enough herd of cattle to make a difference, I can’t believe that a one-shot gimmicky attack would be more valuable than the cow’s value as food, salted and being pulled in a wagon. I’m not convinced that the cows would be any more effective than a heavy cavalry charge, anyway. Big horses and guys with lances/spears/swords makes an impression.
But the OP specifically wanted mounted steers used in the same manner we’d use horses, only with horns. Personally, I’d just attach some spikes to my horse if I was that interested in stabbing things with my mount.
Why not just fly with a plane and drop live sharks over the attacking army instead, or just use a catapult to fire them at long distance?
Similarly to cows stampeding, it would break a small part of the front lines.
The main strength behind the cavalry is not having an animal there on the front lines, it’s giving a person, a soldier increased maneuverability. Capability of the war animal to cause devastation by itself is somewhat secondary in importance.
If I remember right, Mongo rode into town on a Brahma and the peoples ran for cover. “Don’t shoot him, it only makes him mad”
That’s because they’re bad gnus…
OK, the simplest is always the best.
You propose a weapon use.
Do you want to CONTROL that weapon? Or do you prefer it to attack your own force AND the enemy force equally?
Cattle, which IS what a cow ultimately is, are NOT trainable for aggression, they’re visual in response, hence the rodeo clown to divert the behemoth from killing the former rider.
THAT said, I’ve heard of documented cases of driving sheep across a minefield in WWI.
<golf clap> 
Makes for a really lousy Black Sabbath song.