WE tend to think of the mare doing all the work as she delivers her foal, but in reality it’s a team effort! Foaling is divided into three stages (see table).

Stage one may be overlooked as the mare may not seem to be doing very much at this point, although some individuals (especially maidens) may become quite uncomfortable and agitated. However, there is lots of internal activity occurring.

Up until month seven/eight of pregnancy, the foetus is quite small (not much bigger than a football) and has space to move around within the foetal membranes and fluid that surround it.

It then undergoes a very rapid growth spurt and rapidly starts to run out of room. By month 11 the foal is normally in a ‘dog sitting’ position with its muzzle facing the mare’s head, its front legs tucked up against its abdomen and its spine facing the mare’s hindquarters and belly.

The long legs of a foal are needed to ensure it can keep up with its dam from birth. However, they also pose a risk before birth as, if the foal is overly active in late pregnancy, there is a risk of its feet tearing or damaging the now tightly stretched uterine wall.

To avoid this foals have soft, finger-like, projections on their hooves to cushion them.

There is also a hormonal protective mechanism: as the foal runs out of space towards the end of pregnancy its adrenal glands start to produce lots of progestogens (a group of progesterone-like hormones). Progestogens are also produced by the placenta.

These hormones help to keep the strong muscle layers in the wall of the uterus relaxed and reduce the risk of a tear occurring. There is also some evidence that high progestogen levels may induce a sleep-like state in the foal; reducing their activity levels to protect the distended uterus from kicks or stretches.

As foaling approaches, the foal needs to begin to prepare for survival in the outside world. We still don’t fully understand all the details in this process but it features a sequence of hormone changes. A few days before birth, the foal’s adrenal glands suddenly switch from making progestogens to cortisol (the ‘stress hormone’).

Cortisol causes the lungs to mature so that they will rapidly inflate and begin to transport oxygen into the bloodstream when the foal takes its first breath. The fall in progestogen hormones allows uterine contractions to begin.

These are very gentle at first and happen mostly at night during the end of pregnancy.

Eventually, however, the contractions increase in strength and frequency and stage one labour begins.

STAGE ONE

The now more forceful uterine contractions stimulate the foal to twist around and rotate its body along its spine, so that its head and shoulders are now facing towards the mare’s tail. The foal also straightens its front legs and extends its head so that its muzzle is lying along its knees with its spine facing upwards, towards the mare’s back.

After an 11-12 month long pregnancy, this transition to the correct position for birth happens incredibly late in the day, literally just before the foal is born.

The mare may get up and down or roll during stage one and this believed to help position the foal correctly. A YouTube video with footage and animations showing this rotation of the foal during birth can be viewed on www.foalinmare.com

Contractions of the uterus begin at the horn tips and move rhythmically towards the cervix. This pushes the foal within the surrounding membranes and uterine fluid into the pelvis and towards the birth canal. This stretches the tissues around the cervix which stimulates the sudden release of large quantities of another hormone: oxytocin, from the brain.

Oxytocin stimulates the even stronger uterine contractions that will be needed for birth.

As these contractions continue they eventually cause the foetal membranes surrounding the foal to rupture, releasing the fluid surrounding the foal into the vagina. This is known as the waters breaking and indicates that the second stage of labour has begun.

STAGE TWO

As the foal is pushed into the vagina, most mares lie down on their side and begin to strain vigorously. These forceful abdominal contractions help to rapidly push the foal out of the birth canal. The foal is an active participant in this process.

If you have attended many foalings, you may have noticed the foal’s front feet moving back and forth a little as they come into view.

This is the foal moving its elbows and shoulders, seemingly to avoid them getting caught on the edge of the mare’s pelvis.

Because the foal rotates into the birth canal at the last minute, it tends to have one front leg (and hence one shoulder) slightly in front of the other. This reduces the diameter of the foal at its widest point and helps it to pass through the pelvis without getting stuck.

Once the chest and shoulders are free of the birth canal, the foal can take a breath. Oftentimes the mare will take a short rest at this point, before the foal’s hind limbs are delivered.

This allows the remaining blood in the placenta to pass into the foal’s circulation before the mare moves or gets up and breaks the umbilical cord.

STAGE THREE

Uterine contractions continue while oxytocin causes the uterus to contract and shrink.

The mare may experience some abdominal cramps during this process. The placenta detaches from the uterine lining and should be passed in one intact piece within one and two hours.

The oxytocin that is still being released into the mare’s system promotes her to let her milk down, as well as encouraging maternal behavior and bonding with the foal.

PROBLEMS

Given how actively involved the foal is in events before and during birth, it is no surprise that many problem deliveries turn out to involve a foal that was in some way abnormal or compromised.

Minor positional abnormalities, such as a leg bent at the knee or fetlock, or the muzzle down by the shoulder, are typically fairly straightforward to correct.

The foal is pushed back towards the uterus to make room and gently repositioned using a clean, gloved and well-lubricated arm. The delivery can then proceed normally.

However, if the foal has contracted or deformed limbs it will not be able to get itself into the correct position. Oversized foals are uncommon, especially compared to cattle, but a big foal could get stuck at the hips. If this happens, grasp one front leg firmly and pull it upwards, towards the ceiling.

The aim is to lift and rotate the hips over the pelvis one at a time, allowing them to slide out. Premature birth or uterine infections (placentitis) can result in a weak foal that is also at greater risk of a difficult or abnormal birth.

It’s helpful for breeders and stud personnel to have an awareness of what is happening to both the mare and foal as each stage of labour progresses.

This knowledge can help to identify problems as soon as they arise and increase the chances of a successful outcome.

Happily, the vast majority of foals are healthy and able to get themselves into the correct position, ready for an uneventful and rapid arrival (figure 1).

Karen Dunne, MA, CertEM (StudMed), MVB. Veterinary nursing programme director at Dundalk Institute of Technology (DkIT). Member of the education, research and industry (ERI) and equine groups of Veterinary Ireland. My interests include large animal nursing, equine and stud medicine and education.