Blood farms in different parts of the world impregnate horses and draw their blood for the hormone to be injected in other animals. The production of the hormone is increased if the animal is stressed. Videos from the notes might be age or region restricted, here is a invidious link: Iceland - Land of the 5,000 Blood Mares https://invidious.lunar.icu/watch?v=SkHP65O4RUg
Science: Hey, we figured out how to extrapolate data on dinosaur fossil pigments so we have a better understanding of how they appeared and thus evolved.
Also Science: We make these horses live in constant stress and impregnate them artificially so they produce a hormone that we extract through their blood so we can inject said hormone into other animals.