With spring comes renewal and the promise of new life, from snowdrops and buds on the trees to lambs in the fields. Foals are also part of nature’s cycle at this time of year.
Why don’t mares give birth all year round?
For an answer we need to look far back in time. It has been argued that horses are the last of the mega-fauna that existed during the Ice Age that ended 12,000 years ago. Woolly mammoths and woolly rhinoceros, Irish elk and aurochs, a type of cattle, all died out. Horses, which had originated in North America, died out there, but survived on the Steppe of Asia.
As an Ice Age animal horses were adapted to live in very harsh conditions with extremely cold winters, with a lack of grazing feed. These kind of conditions still exist where pockets of wild horses exist, for example mustangs on the plains of America and Przewalski horses on the Steppe.
If foals were born in autumn or winter into this kind of environment, the chances of survival would be virtually zero so horses are seasonal breeders.
The fertility cycle and gestation (pregnancy) period of horses is such that they are fertile in spring and early summer to give birth the following spring/early summer. This ensures the foal is born when it is warmer, with an abundance of grazing for the mare to use to produce milk.
Mares can also come into season extremely quickly after giving birth, the ‘Foal Heat’. Wild horse mares would be pregnant all the time whilst raising the foal.
So what does that mean for keeping horses now?
Careful consideration should be given to the breeding of mares. Bringing an unwanted foal into the world will be a drain on financial resources and require a large commitment of time in caring for both the mare and the foal. Unfortunately, too many foals are born without this consideration, which benefits neither horse nor man.
The age and health of the mare should be taken into account. From the age of 15 the fertility of mares reduces by 50 per cent every year, so a mare at 17 will be only 12.5 per cent as fertile as a horse at 15 years old.
Mares should be generally healthy, without any conditions that may affect the mare or foal during pregnancy. If you have any doubts about this, please contact the practice and we can discuss your requirements.
Sandy Baird, Vet.