I had never heard of this tradition (which some see as animal torture, akin to bullfighting) before. It takes place in the villages of northwestern Spain in the 'Galicia' region. No, not that 'Galicia' if you're thinking of Poland and further east. Galicia in Spain gets its name from Celtic settlers and Galicia - whose borders are a little vague - gets its name from a village called 'Galicja'
Wiki for 'Galicia (Eastern Europe)' - a disputed title, by the way here.
Wiki for 'Galicia (Spain) here.
So...let's talk about the 'Rapa das Bestas'.
As you'll see from the video, it's a real struggle between the villagers who wrestle the horses to the ground so that their manes can be sheared and they can be outfitted with identification tags but it also doesn't take long and the animals are not permanently damaged. It's necessary, according to the practice's defenders, because the horses are wild in the woods near the village 364 other days of the year.
PETA doesn't like it at all.
Here's a Wiki on 'Rapa das Bestas'
The video was made by Ruptly.tv