How much can the gestation period in horses vary while still being considered normal?

In horses, the typical gestation period ranges from about 320 to 380 days, with the average being around 340 days. However, it is recognized that variations within this range can occur while still being considered normal. A variation of up to 30 days allows for natural differences between individual mares, which can be influenced by several factors including breed, age, health, and environmental conditions.

This 30-day range is significant because it accounts for the natural biological variability in reproduction among horses. While shorter or longer gestation times can raise concerns, a variation of 30 days encompasses the acceptable limits for gestation length in mares. This understanding is crucial for breeders and veterinarians in monitoring the health and well-being of both the mare and the upcoming foal.