A Pictorial Guide to Late Term Development of the Pregnant Mare

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The following article is a guide aimed to give the novice breeder an insight into the late term development of the pregnant mare. Every mare, like every woman, develops differently and, without access to a large number of broodmares, it can be a little confusing in assessing the development of the mare as she approaches foaling.

The final month before birth

The following mares are all due to foal within six weeks or so of the photos being taken. Mare 1 has a last service date that would indicate that she is due within the next seven days, She is not a maiden and has teats that suggest this. Pic 1

Note how the bag is beginning to fill. At this stage, it will feel firm and rounded, but on palpitation, no milk can be expressed and she is yet to wax up. She also has the beginnings of development of the veins that supply blood to the teats; these will become very developed as birth becomes imminent.

Mare 2 has a ‘due’ date within the next 28 days. She has had a bag of this size for two weeks which led us to believe that she was going to foal well before her date but over the week before this photo was taken the development of the bag had slowed and stopped. It is not shrinking in size but not changing either; again, she is not a maiden. Mares sometimes make a move on developing a bag well before their due date, and this should be monitored. If milk can be expressed well before the due date, this is a matter of concern as the mare may be aborting.  Pic 2

Mare 3 is due around the same time as mare 2 but she had only recently developed any sign of her bag filling. Again she is not a maiden.  Pic 3

Mare 4 is due around 6 weeks after this photo was taken, she has a tiny bag and although not a maiden it is not immediately apparently that she has had a foal before. Last season was her first foal and she did not develop any sign of bag until an hour before foaling, when she waxed up. The foal had to be ‘tubed’ with donor colostrums from the stud’s own bank because despite her colostrum testing to a good standard, with teats so small it was difficult for the foal to get the vital colostrum off his mother. She also failed to provide much milk and the foal weaned himself onto solids very quickly. It is vital in a case such as this to monitor whether the foal is nursing as this encourages the mare to produce more milk.  Pic 4

Waxing Up

Waxing up can occur anytime within the last month of birth. Some mares will wax up really early whilst others will only wax up within a hour or so before foaling. Initially it will appear as a clear sticky fluid in a blob on the end of each teat. This will increase to a definite clear waxy substance around each teat. When birth is close the wax will turn from clear to yellow to white. At this point milk can usually be expressed upon palpitation.

Mare 1 – 2 days prior to birth, the wax is milky in appearance.  Pic 5

At this point she slackens off behind quite significantly and her pelvis opened as shown in Pic 6
Pic 7

This mare is still stitched; this is stud procedure although I would strongly recommend that the private breeder has any stitches opened a month prior to foaling.

And at birth – the wax has fallen off and the milk can clearly be seen, this mare actually was squirting milk with each contraction. Pic 8

Here is Mare 4 once labour had started; there was no sign of wax 4 hours prior to birth. Pic 9

And so there are no hard fast rules for how a mare should develop, but I hope that this pictorial guide has shown the variations that can be seen. I tend to feel the teats every day to see if any fluid is present and to gauge the fullness and firmness. As shown some mares can move on very quickly and so it is essential to record what your mare does as they tend to follow the same routines. Mare 3, once again, nearly caught us out; she had no wax prior to birth and also did not pace the box. This is the third year that she has done this, choosing to sleep for a long time, then get up and lie down, then foal with minimum fuss.

And the end result we are all hoping for..... (Mare 1)  Pic 10

Note how slack the bag now looks, due to the foal nursing. After foaling it is vital to check that the foal is ‘on suck’. If the mare’s bag is dry or appears to be swollen and hard this is indicative of the foal being off colour and further investigation is necessary. Failure to do this can lead to problems with the foal, and mastitis in the mare. The following photo is one of a mare that has suffered severe mastitis in the past, which was not adequately treated. The teat was very difficult for the foal to suck from and required ‘stripping’ (milking) to make the mare comfortable and get it to a size where the foal could get the teat into her mouth.  Pic 11

Good luck on a successful and stress free foaling!  Pic 12

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