Fake. Horse jizz doesn't have the consistency of sour cream/cake frosting.
The real thing isn't all that much different than human jizz, except in the quantity "dispensed", which is MUCH larger than a human spooge.
I've also never in my 50-ish years of dealing with horses, including plenty of time in the breeding/collecting shed, encountered a stallion that's anything other than rock-hard/stiff-as-a-board and at least partly flared when he blows his load. The horse in this footage is on the verge of "floppy". A couple of places, the bimbo comes damned close to folding his dick in half - Something that is simply impossible to do with a horse that's on the verge of ejaculation.
Then there's the reality that it's not quite, but mighty damned close to it, impossible to bring a stallion to ejaculation with the manipulation this bimbo is using. They just plain "don't work like humans", and don't respond well to the sort of "stimulation" we see in this farce - Any horse I've ever dealt with in the shed would either go completely flaccid and "reel it in", kick/stomp/slam/bite the perpetrator (or at least make the attempt) or some combination of all three.
This footage is a pure bullshit fake "cumshot", put together for one purpose, and one purpose only: To separate clueless folk from their money. There is no amount of reality at all involved.