Horses can not process meat in any way, they do not seek it. Some clueless people give hamburgers as treats, but the horse is only after the bread, the meat does nothing except interfere with their digestion.
Horses are prey animals so everything they do centers around defense. They will attack predators only when the animal has seemed to pursue, and running is not the best solution.
When they rarely go after coyotes, mountain lions, and snakes, they seize it and shake it to death.
My very sweet horse in my avatar once grabbed up my small JRT dog when he got underfoot while we were training. They both got along wonderfully but those defensive instincts were triggered by what doggo thought was fun.
He grabbed him up by one back leg and then froze with his head high in the air.
Doggy was dangling upside down in the air and my horse looked shocked that there was something unpleasant in his mouth.
When a horse is frightened their jaw will lock, it's a physiological response.
I yelled "No, drop him!" and my horse just looked more scared. I regained my senses and walked up to him with a soothing tone saying, "It's okay" and his jaw unlocked.
Doggie fell down and ran around, when I got him to hold still there was not a mark on him. He didn't get a bruise or even tenderness on his leg.
Horses don't want to hurt anything. They simply want to avoid being hurt.
As a predator species it requires some mind warping from humans just to partially comprehend how different horses are. It's easier for us with dogs, cats, and even chickens.
So, I don't know what exactly was going on in that video, but I'm 100% certain the horse did not set out to eat a chick. Odds are on the human setting this up.