Your horse is 370 days pregnant when do you worry?

Answer 1

Good question. While 370 days is well within an acceptable range, there are multiple issues to consider when determining whether to worry or not.

1) Is/are the actual breeding date(s) known? Realize that the mare could ovulate 2-3 days after she was last bred. If pasture bred she may have cycled back in without being observed and the gestational age of the foal could be 20 or more days different than the breeder realizes.

2) The mare could be carrying twins. Because twins get only half of the nutrition normally given to a single foal maturation is slower. Most breeders will insure that

twin pregnancies are eliminated early in the breeding process (at 14-16 days post ovulation) because successful foaling of two live twins is actually quite rare and because the possible complications (abortion, dystocia, etc.) result in both economic and emotional loss due to veterinary costs or death/injury of/to the mare or foal(s).

Generally, mares that produce twins (succesfully or not) are also more likely to lose the subsequent breeding season.

3) If the mare is older her foal may require additional time to mature because of wear and tear on the uterus.

4) Breeding dates were inaccurately recorded or mixed up with another mare.

5) If the mare was poorly nourished or ill at some point during the pregnancy foaling

can be delayed.

These are the most likely causes of prolonged gestation that are not, in and of themselves, a cause for worry.

Other possible causes that are more concerning.

1) Fescue toxicosis

2) Exposure to spoiled/moldy corn based products. This results in a prolonged gestational period and large, limp (dysmature) foals.

3) Wry foal, body pregnancy, hydroallantois (often these foals are premature but not always).

4) Other (rarer yet) issues. (That's helpful isn't it?)

Finally, since the question about whether or not to worry (you are already worried, right?) is being asked, the mare owner needs think about their level of experience and determine if the best course of action is to get an opinion on the status of the mare and her foal from a veterinarian or more experienced horseperson. There is a lot of time, energy and emotion already expended while waiting for this mare to foal

a little money spent now to be reassured (or forewarned) is probably well worth it.