Milk Test Strips

Everyone in the business of breeding and raising horses has gone through the anticipation of the foaling event. All of the preparation work has been done. The breeding dates were carefully recorded. All of the conceivable formulas for determining the theoretical foaling date have been utilized. All of the barn yard advice has been collected. “Don’t leave home for two weeks prior to the foaling date.” “Check on the mare on a two hour schedule round the clock as the foaling date approaches.” “You must be present at the foaling to be sure that the foal does not suffocate in the amniotic sac.” Short of setting up camp with the expectant mare or investing in a significant amount of hi-tech gear such as closed circuit TV and alarm systems, what can a person do to get a better handle on when a mare is going to foal.
The first thing that we can say is that regardless of what steps that a person takes, Mother Nature still has the upper hand on determining the actual onset of foaling event. We can, however, help ourselves out in a number of ways to get a hint as to what may be going on.
A few years ago some ingenious person must have evaluated how mare’s milk changed as she approached foaling. What they determined was that as the mare gets closer to birth, the quantity of calcium in her milk increases. Someone then remembered that water hardness is a measure of the calcium content in a water sample. Put the two together with a little calibrating and we have a tool for easily measuring the increase of calcium in the mare’s milk and, theoretically, a way of predicting foaling. That is exactly what has occurred. A number of different water hardness test strips have now been calibrated and are being marketed as foal predicting tools. Since then we have also utilized narrow range pH test strips as an additional tool
We have been using milk test strips for a number of years as part of our pre-foaling routine. They have been useful in gaining an insight as to how each mare is progressing toward foaling. They definitely provide a picture into the physiological changes that are going on with each mare. We have advised many folks to use milk test strips with their foaling programs. Some have felt they are very useful others have been disappointed.
The biggest disappointment that seems to arise from the use of milk test strips is they graphically point out that horses do not read textbooks when it comes to foaling. Many people get it in their mind the predicted foaling date is when you go open the valve on the mare and the foal comes out. Unfortunately, as stated earlier, Mother Nature keeps that little secret to herself. The theoretical foaling date is usually the center of a range of time when foaling could occur. The milk test strips also point out that the calcium level in a mare’s milk does not increase in a regular way. The way that calcium increases in the milk from one mare may be completely different from the way that it changes in another. For those who are looking for an easy or foolproof absolute, milk test strips are not.
The great thing about using milk test strips is that they provide additional information to the person who is observing the expectant mare. Add this information together with other changes such as udder development, changes in milk color, viscosity to touch, mare behavior changes and milk test strips provide a valuable addition to the arsenal of information the observant broodmare manager uses to narrow down the mare’s foaling time.
Obviously, the use of milk test strips is predicated on the ability to obtain small samples of milk from the mare periodically, prior to foaling. Once again, obtaining milk is somewhat individual based on the mare. Generally speaking, however, enough milk for testing (approx. 1 cc. per test) can be drawn from most mares. With miniature horses the exception is with maiden mares. Those mares that have not yet produced a foal usually do not produce milk until just (meaning hours) before the foal is born. We have had difficulty using milk test strips with maiden mares. We generally rely on the actual presence of a measurable amount of milk being produced by maiden mares as our indicator that foaling is imminent.
We use two types of tests to aid us in determining the mare’s readiness to foal.  One is essentially a measurement of the quantity of calcium present in the mare’s milk and the other is the pH of the milk.  When used together these two tests have been quite helpful as indicators to when a mare will foal.
Obtaining the test strips has been somewhat difficult over the years based on different suppliers business status.  As of this writing Fisher Scientific Co. has the two strips that we use available for ordering by the general public.  The strips can be ordered directly over the internet by going to You will need to create a username and password to access the catalog information, however this takes very little time.
The two strips we order are as follows:
Catalog No. M100251,  EM Quant Test Strip – Total Hardness (40-230 ppm)  These come packaged 100 strips to a vial and need to be refrigerated to maintain their shelf life
Catalog No. 0987620,  Whatman Type CS Test Strips (pH Range 6.0 – 8.1),  Whatman number 2629-990.  These come 200 strips to the package.  Make sure you keep these strips in a sealed container such as a plastic bag and away from any chemicals or fumes that may effect their measurement.
The additional supplies you will need are:
1. Distilled Water
2. Small Collection vial for taking milk from mare (we use clean
prescription pill bottle)
3. Test tube for putting the milk and distilled water into
4. Two syringes for accurately measuring the water and milk. (we use a 1ml insulin syringe for measuring the milk and a 6ml syringe for measuring the distilled water.
A.  The procedure is quite simple. Obtain a small amount of milk from the mare by stripping it from one of her nipples. Usually you can be successful by gently squeezing slightly above the nipple then drawing your fingers down toward the tip of the nipple. You should collect at least 1 ml because that is what is needed for the test. Usually you can get a couple of mls.
B.  Measure accurately 6ml of distilled water using one of the syringes and put this into the test tube.
C.  Accurately measure 1ml of the mare’s milk using the other syringe and deposit it into the test tube.
D.  Shake the test tube vigorously to mix the milk and distilled water.
E.  To test for the CALCIUM content in the mare’s milk, use the EM Quant strip that has 4 green spots on it.
F.  Take a test strip and completely immerse the colored patches in the test tube for 2 seconds.
G.  Remove the strip and give it a shake to remove any excess liquid.
H.  Read the color changes in the 4 patches after waiting 1 minute.
Keep in mind that the trick in using these is the interpretation of color change and putting this information with other signs that your mare is giving you such as bag fullness, milk consistency and color, tail laxity, and past foaling history if you know it.
Each mare is different and all do not go by the rule of thumb. Knowing that I will give you the general trend that we have seen with our miniature horses. If three of the patches turn from green to purple within the minute and the 4th shows very little sign of change chances are that the mare isn’t quite ready. If three change color and the 4th turns 1/2 way from green to purple, we start watching her pretty closely however it doesn’t necessarily mean that she will foal in the next day either. If all 4 patches turn color in less than one minute chances are that the mare will foal within the day.
Use the same milk/distilled water solution to test the pH level of the mare’s milk.   Use the Whatman strip for this test.  Immerse the strip into the fluid as above to completely cover all of the indicator bands.  This test can be read more or less immediately.
The general trend is that a mare’s milk will test above pH 7 for a period of time before foaling and as she approaches foaling the pH level will drop.   When the milk is pH 7.0 or below she is getting close to foaling.  Most of our mares foal within a matter of hours to a day when the pH level goes to 6.8 or below.
When combining the results of the Calcium and pH tests they give you another indicator as to the mare’s readiness to foal.
We check our mares every evening. With the preponderance of mares foaling at night we get the most current information by testing in this manner. I can’t emphasize enough, however, that milk test strips are not the end all for predicting foaling. We use them to provide us with one more bit of information to put with all of the other observations we are making of the mare.
The best tool still remains the hardest to follow through with.  That is CONSTANT AND UN-RELENTING VIGILANCE WITH ATTENDANCE  AT EACH FOALING. If you can endure this difficult requirement and utilize the various tools such as milk test strips to inform your self, the odds are increased for a favorable outcome for your mare, the new foal, and yourself.