A group of Mares is known as a stud, the name given to Mares that are kept together for breeding. The word “stud” traces back to the Old English “stod”, a term for a group of horses. It originally described any horses gathered together for breeding, and over time it narrowed to mean a group of Mares in particular.
What Is a Group of Mares Called? – Mares Collective Nouns.
