Broodmare Weight GainBy Kentucky Equine Research Staff · February 8, 2010
A study conducted on a Thoroughbred breeding farm showed that initial broodmare body weight averaged 1,272 pounds (577 kilograms), with an average weight of 1,448 pounds (657 kilograms) at the end of gestation.
Assuming average newborn foal weight of around 110 pounds (50 kilograms), mares gained about 66 pounds (30 kilograms) in addition to the weight of the foal. This is a total increase of 13% to 14%, of which most of the weight was gained between the fifth and ninth months, according to this study.
When mares were weighed a month after giving birth, those less than 8 years old were heavier than their initial weight, while mares more than 8 years old had returned to their initial weight. Gain in mid-pregnancy may guarantee energy to support foaling and milk production.