Oh right, the IRL horse had mastitis and galactorrhea... as a 2-year old filly while training for her debut. In other words, she was lactating without being pregnant, and suffered inflammation of her udders at the same time, likely from blocked milk ducts. Treatment for this would usually involve administration of antibiotics along with expressing the milk to relieve the pent-up pressure.

The uma equivalent would be a teen... you know what let's just leave this part unsaid.

Don't think this tidbit of horse trivia is well known among the Japanese fanbase (it's ultimately sourced to a throwaway quote from Bouquet's trainer in a keiba article summarizing her peers), but for some reason nearly everyone in the Korean fanbase knows this with Dcinside users endlessly copypasta-ing this trivia and Namu Wiki headlining it in Uma!Bouquet's article like it's the most well-known "fact" for her.