Here's why:
* Maturity: Horses typically reach sexual maturity around 1 to 2 years old, but they are not physically mature enough to safely carry and give birth until they are older.
* Pregnancy: A mare's gestation period is around 11 months. A 1-year-old horse would still be a foal itself and not ready for the physical demands of pregnancy.
* Health Risks: A young mare giving birth could be very dangerous for both the mare and the foal. The mare's body might not be fully developed to handle the pregnancy and delivery, and the foal could be born prematurely and have health issues.
It's important to remember: Breeding horses is a serious responsibility. It's crucial to wait until the mare is physically and mentally mature to ensure the health and well-being of both the mother and the foal.