Predicting when a mare will give birth
Mares have a very big window as to when they will foal. Maturity can be as early
as 320 days and a normal foal can birth at a year! Most use 332-342 days as the
target date and many mares tend to be consistently early from year to year.
The traditional methods of observing her behavior, monitoring her udder and teat
development, for waxing at the tip of the teats and relaxation of the tail head will
always be a very important part of knowing when a mare will foal. Additionally
there are milk tests than can be performed which can assist us in narrowing down
the day. Occasionally a mare will not allow you to milk her or she does not
produce enough to test and the traditional methods become even more
important. Some will also use a degree drop in temperature as an indicator to
impending birth (24 hours), though accuracy is not as good as mild testing.
Milk tests
There are 2 kinds: a Calcium test (water hardness test), and a pH test. Some water
hardness test strips also test Mg which can interfere somewhat with
interpretation. Both test strips need to be used within their expiration dates and
kept out of extreme temperatures as well as humidity. Also make sure the test
strips measure the appropriate ranges
Calcium test
Test strip range: 50ppm-350+ ppm
Foal prediction:
IF Ca+ < 200ppm the chances of foaling in 24 hours are 99%, and in 72 hours
80%.
IF Ca+ > 200ppm the chances of foaling in 24 hours are 50%, in 48 hours 85%, and
in 72 hours 97%.
IF the Ca+ is less than 400 ug/g there is a 98% chance she will not foal.
IF Ca+ is > 400ug/g (ppm) then there is a 94% chance the mare will foal in 24
hours.
pH
Test strip range: 6.2- 8.0.
Foal prediction:
IF: pH <7 mare 7 of 11 mares will foal within 24 hours. Usually a significant drop
is seen within 24 hours.
IF: pH < 6.4 there is a 98% chance the mare will foal in 24 hours. If less than 6.4
there is also a high chance she will not foal in 24 hours.
Places to find strips
These are examples of items that can be used.
Calcium tests
 Equine specific tests:
o Predict a Foal Animal Health products 800-689-7601
www.ahcpi.com Jeffers http://www.jefferspet.com/predict-afoal/camid/equ/cp/13670/
o Mare foaling predictor kit Valley Vet supply
www.valleyvet.com
 You want a test strip that measures a range of 50-400 ppm the more
accurate the better.
 AquaChek Total Hardness Product #561220 (measures full range)
pH test strips
You can find on line, at Amazon.com or any store that sells aquarium or pool
tests. You want a strip that tests a pH between 6.2-8. (Too wide a range is hard to
see changes).
 pHydrion 5.5-8.0 range www.microessentiallab.com
 API low PH strips 6.0-7.4 range