Taming a equus is a passive tame not a knock out. You'll need to make a trap so it won't run off and get killed. You'll need as much berries as the DeX says. And have a ghillie suit to not spook it.But in case you accidently mount off and lose some taming effect have some more berries with you just in case. This is how I did it.
Run run run, crouch when close still approaching at an angle, when close enough,(stack of carrots in zero slot) click three “e” three times; one to feed, one to mount, one to start THE RIDE! Each time you get the feed prompt, hit “e” and pray it gets stuck in a corner and doesn’t run off a cliff, or into carnivores. Ignore everything but the prompt, hitting “e” without hesitation. (You cannot control the run at all). That’s it.