Development of a Horse Fetus

A horse fetus takes about 11 months to fully form, and is usually born 334 to 340 days after conception. A foal born before 326 days is considered premature, and a horse born before 310 days has very low chances for survival.

  1. Growth

    • By 24 days gestation, the embryonic vesicle is 1 inch in diameter and has a beating heart. By day 100, the horse fetus is 7 inches long with ½ inch long ears and ¼ inch hooves.

    Development

    • A fetus 150 days old gains a pound every 10 days, is the size of a rabbit, and has hair on its chin, muzzle and eyelids.

    Features

    • The horse fetus is mostly developed and looks like a foal by day 270, but it has a lot of growing to do before it can survive outside its mother's womb. The lungs are capable of breathing and the legs strong enough to stand around day 320.

    Time Frame

    • The gender of the horse fetus can be determined by ultrasound between days 59 and 68. Day 40 is the end of the embryonic stage and the beginning of the fetus stage.

    Considerations

    • The sire can affect the gestation length, with some sires consistently fathering foals with a gestation length of 340 days or less and others 350 days or more.