Horse Guides – Ask the Expert

 The gestation length of a mare varies from about 330 to 370 days.  Mares will foal when they are ready, often the date of foaling is influenced by the weather and the time of year.  Earlier in the year mares usually foal late, at the end of the summer they tend to foal early.  Development of a bag is one of the indicators of impending foaling along with slackening of the pelvic ligaments and the visual rise in the height of the tail head, in conjunction with lengthening of the vulva.  Production of wax on the teat can be a late stage indicator of impending foaling but not always.  Maiden mares often do not give much warning of impending foaling, older mares that have had a foal or 2 may bag up early.  To accurately predict the date that foaling will occur is difficult hence much time spent observing foaling mares and the use of warning aids such as sweat and vulva alarms.  Milk secretions can be checked for electrolyte levels to see if they will give an indicator of when foaling is likely.  One word of warning is that premature udder development can be linked to conditions to do with the pregnancy such as placentitis – as such it is important to look for other signs of problems such as a vulval discharge.  If you are at all uncertain contact your vet.

Regards,

Ed Lyall

Ed Lyall is a partner in the 15 vet Arundel Equine Hospital LLP, based in West Sussex.  He is interested primarily in reproductive medicine, including artificial insemination and embryo transfer, as well as sport horse performance management.  The practice provides a full ambulatory service to East and West Sussex as well as into Surrey and Hampshire.  The on the road vets are backed up by a full hospital including bone scan and surgical facilities, as well as an onsite laboratory.  All types of horses and ponies are cared for.