How to measure the sugar content in hay yourself
The sugar contents reported in the literature are always based on dry matter. With hay you can assume that your measurement is reasonably close (possibly deviating 1-2% from the value measured in the laboratory) of the actual dry matter. We checked this with several tests of different hay batches. With grass you have to calculate with different amounts, because it has a higher moisture content. You can assume that 100 grams of grass would be about 20-25 grams of hay. That means you have to multiply the measured sugar content by 4 or 5 (lush grass x5, drier grass x4) to get the global value in dry matter.
Calculation example: 100g of fresh, juicy grass from the meadow has a sugar content of 8%, which corresponds to 80g in a kilo of this grass. 1 kilo of this grass turnsinto approx. 200g of hay, when dried. So you have to do the measured value (80g) times 5: 80×5 = 400g sugar in 1kg hay. Then you have converted the estimated value to dry matter, so 400g sugar compounds in 1kg dry matter.
The literature indicates that horses take in 40-50kg of grass when grazing 24/7 (which corresponds to 10kg of hay). With a sugar content of 8% (=80g/kg) in fresh grass, we are talking about 3,200 – 4,000g of sugar, which is then absorbed in 24 hours. There is some evidence that only about 25% of it is present as mono- and disaccharides, ie as single or double sugars, which are absorbed directly into the blood as sugar directly in the small intestine.
Some of the soluble sugar is also in compounds that cannot be digested in the small intestine. For example, fructan, which is not super healthy, but has no direct influence on blood sugar levels. So if you assume that in our calculation example about 25% of the measured sugar compounds are mono- and disaccharides, you are talking about 1 kg of sugar intake in 24 hours. So a whole bag of household sugar, such as you can buy in the supermarket.
For horses, hay with a sugar content of less than 10% is usually recommended. For horses that are extra sensitive to sugar or have a metabolic problem, below 6%. So if you assume a ration of 10kg of hay, no more than 1kg or 600g of that should be sugar.
If your horse grazes for a shorter period of time, say just 1 hour a day, they can increase their eating speed and eat up to 4 times faster. This means that instead of 2 kg per hour with 24/7 grazing, they can absorb 8 kg per hour if they are on the meadow for 1 hour a day.
Then we are talking about 640g of sugar compounds in our example. Even if only about 160g (25%) of it goes straight into the blood as sugar, that's a significant amount in a short period of time. For comparison: 1 sugar cube is about 3g. That's more than 50 sugar cubes in an hour.
It is therefore also wise to test not only your hay, but also the vegetation in your meadow for sugar content. The lower the better for the horses. If you have a vegetation of austere grasses and herbs in the meadow, you will soon reach a sugar content of 2-3%. That has a very different effect on blood sugar than a meadow with sugar-rich grass (perennial ryegrass can contain up to 36% sugar!).
Also the next time you buy hay, you can make a quick estimate of the sugar content with the refractometer. After that, decide whether you want to buy this hay lot or whether it is too sugary.
How do you determine the sugar content?
· 50 to 100 grams of hay
· Digital kitchen scale with a measuring accuracy of +/- 1g
· Freezer bag of 3L
· Wine refractometer with 0 – 32% Brix (example: https://amzn.to/37oFArc )
· garlic press
· Clean plate/bowl
· Transfer pipette (pasteur pipette; usually supplied with the refractometer)
Step 1. Remove the hay from different parts of the bale and mix it well. Set the scale with the freezer bag on it to 0 (tare). This so that the weight of the bag is subtracted from the measured weight (or record the weight of the bag and subtract it from the measured weight later). Put 50-100g of hay sample in the bag and weigh it.
Note: To get an average value, several bales from different parts of the meadow must be measured separately. You can then calculate the average of those different values.
Step 2. Add the same amount of water to the hay in the bag. So with 50g of hay, add 50g of water. When adding the water, if possible, wet all the hay and then “knead” the closed bag a little. Make sure that no water is lost and that the bag is not damaged.
Step 3. Distribute/spread the hay in the bag, release the air from the bag and close the bag. Then leave it under, for example, a book for an hour. After approx. 30 minutes turn the bag over, knead again if necessary and then distribute/spread the hay in the bag again and put it back under the book. Alternatively, the bag can also be frozen immediately and measured later. But then the bag must also be weighted down with something when freezing, so that the water evenly wets the hay.
Step 4. After an hour (if the hay was frozen, it should thaw for about 45 minutes), put a small portion of the hay in a garlic press and squeeze it onto a plate.
Note: If only 1 or 2 drops can be squeezed out, you can drop them directly onto the refractometer. If more drops come out, first drop them on the plate and then apply 2-3 drops of this to the refractometer with the transfer pipette (pasteur pipette).
Step 5. Close the refractometer lid and read the sugar content on the scale
Step 6. Repeat steps 4 and 5 several times and calculate the average from the measured values. Between measurements, wipe the refractometer and the plate with a soft cloth so that there is no residual liquid from the previous sample. Also make sure that there are no liquid residues in the transfer pipette, if necessary rinse it with tap water in between and then remove as much water as possible.