I'm guessing they harvested his sperm? Because no way any normal male horse could fuck 1000+ female horses
Nope, all 1243 + 1 (Vodka) were live covers.
Throughbreds must be conceived live in order to be registered as throughbreds. Live cover here means purely "natural" stallion on mare action; no artificial insemination, no assisted reproductive techniques, nada.
Usually a "hardworking" breeding stallion can cover 100-200 mares per year in their prime. Really popular ones can even go up to 400 and more, though some countries now try to limit this number in an effort to broaden the gene pool.
Tanino Gimlet worked as a breeding stud for 17 years, so being able to cover 1000+ mares isn't really surprising.
Wonder how many sibling vodka has irl that came from gimlet
Since only the horses that the mother foals counts as siblings in the equine world, Vodka would only have 8 siblings, with only 2 of them being full siblings (as in the mother and father being the same horse).
That doesn't mean Gimlet is not responsible for 1241 other progenies though...