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The fact that the sugar content in roughage is a critical factor in horse feeding is becoming more and more widely known among horse owners and stable owners. But how do I know how much sugar is in my hay? Or in the grass on my pasture?

Especially when transitioning the horses to grass pasture, ithe risk of laminitis due to high sugar levels in the grass, especially if insulin resistance is undetected, should not be underestimated.

To know how much sugar is in the forage, one usually takes samples of the forage in question and then sends them to one of the agricultural testing laboratories to have them analysed. Depending on the workload, it usually takes one to two weeks to get the results. During this time, however, the sugar content in the pasture can have changed significantly, because it fluctuates not only with the growth, but also in the course of the day, from day to day and above all with the weather.

This means that two weeks later the sugar content can already look completely different from the day the samples were taken. This period is of course also often too long when it comes to deciding to buy a batch of hay, because in the meantime the farmer has often already sold the hay elsewhere.

A simple alternative to determining the sugar content of hay

Elke Malenke has developed an ingenious and simple method to determine the sugar content of hay with the help of a commercial refractometer. We have prepared the instructions for you in a way that every horse owner or stable operator can easily do it themselves.

It is even easier to determine the sugar content in grass. All you have to do is cut off the fresh grass, weigh it, squeeze it and put the drops directly on the refractometer. And just like that, you have an approximate idea of the sugar content of your pasture.

Of course, the sugar content given in the literature is always based on dry matter. In the case of hay, you can assume that your measurement is fairly close to the actual value in dry matter, possibly 1-2 % different from the value measured in the laboratory. We have checked this with several tests of different hay batches.

With grass, you have to reckon with other quantities, as it has a higher moisture content. You can roughly assume that 100 g of fresh grass would become 20-25 g of hay once dried. This means that you have to take the measured sugar content times 4 or times 5 (juicy grass x 5, drier grass x 4) to get approximately the value in dry matter.

A calculation example:

100 g of fresh, juicy grass from your pasture show you a sugar value of 8 %, which corresponds to 80 g in a kilo of this fresh, juicy grass. If dried, 1,000 g of this grass would make about 200 g of hay. So you have to take the measured value (80 g) times 5: 80×5 = 400 g sugar in 1 kg hay. This gives you the approximate value converted to dry matter, i.e. 400 g sugar compounds in 1 kg dry matter.

The literature states that horses consume 40-50 kg of grass during 24 hours of grazing (which in turn would correspond to about 10 kg of hay). At 8% sugar content (=80 g/kg) of fresh grass, we are therefore talking about 3,200 – 4,000g of sugar that are absorbed in 24h. There are indications that only about 25% of this is present as mono- and disaccharides, i.e. as single or double sugars, which are absorbed directly into the blood as sugars in the small intestine.

This is because some of the soluble sugar is also present in non-small intestine digestible compounds such as fructan, which are not super healthy, but at least in most cases have no direct effect on blood sugar levels. So if we assume that in our calculation example about 25% of the measured sugar compounds are present as monosaccharides and disaccharides, we would be talking about about about 1kg of sugar intake in 24h. In other words, a complete packet of household sugar, as you would buy it in the supermarket.

For horses, it is usually recommended that hay should have a sugar content of <10%, and <6% for horses with metabolic disorders or sensitivities. So if we assume a ration of 10 kg of hay, no more than 1 kg or 600 g of it should be sugar. With our earlier calculation example, it’s not looking good.

Sugar intake for the horse

Especially if we assume that horses eat more hastily when grazing for a shorter period of time and can increase their eating speed fourfold. So instead of taking in around 2kg per hour (as it would with free range 24h grazing), the amount can increase to 8kg of fresh grass in one hour if the horse is only put out to pasture for that one hour.

In our example, we are talking about 640g of sugar compounds. Even if only about 160g (25%) of this goes directly into the blood as sugar, that is a considerable portion in such a short time.
For comparison: 1 sugar cube has about 3g. So that would be over 50 sugar cubes in one hour.

Relatively little effort provides information about the sugar content

It is therefore worth testing not only the hay but also the grass on the pasture for its sugar content. The lower the sugar content, the better for the horses. If you have a pasture full of lean grasses and herbs, it’s easy to get sugar contents of only 2-3%. This makes a considerable difference in the effects on blood sugar levels compared to a pasture with high-sugar grasses (in perennial ryegrass, the sugar contents are up to 36%!).

And the next time you buy hay, which will be in the summer, you can quickly determine the sugar content with your refractometer and then decide whether you want to buy this batch or whether it is too high in sugar for your herd, which already tends to be overweight and at risk of disease.

Quick and easy sugar determination in hay – for horse owners & stable operators, method by Elke Malenke

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Needed materials:

  • 50 to 100 g hay per sample to be measured
  • Digital kitchen scales with a measuring accuracy of +/- 1g
  • Freezer bag (3L)
  • Wine refractometer with 0 – 32 % Brix (source of supply e.g.:
  • Garlic press
  • Clean plate or bowl
  • Transfer pipette (Pasteur pipette; usually included with the refractometer)


1. Take hay from different parts of the bale and mix. Tare the scale with the empty freezer on it, to ensure that the weight of the freezer bag is subtracted from the reading (alternatively, note the weight of the empty bag and subtract it from the reading later). Place 50-100 g of the hay sample in the freezer bag, weigh.

Note: To obtain an average value for a pasture, several bales from different parts of the pasture should be measured individually and an average value calculated at the end.

2. Add the same amount of tap water to the hay in the freezer bag. So for 50 g of hay, add 50 g of water. When adding water, wet all the hay if possible and then “knead” the closed bag a little. Be careful not to lose any water or damage the bag.

3. Distribute the hay in the bag, let the air escape from the bag and close it. Then leave for an hour weighed down with e.g. a book. After approx. 30 minutes, turn the bag over once, knead it again if necessary and then distribute the hay in the bag again and weigh it down. Alternatively, the bag can be frozen and measured later. However, it should also be weighed down for freezing so that the water wets the hay evenly.


4. After one hour (if the hay was frozen, it must thaw for around 45 min) put a small part of the hay into a garlic press and squeeze it out onto a small plate.

Note: If only 1-2 drops can be squeezed out, they can always be dropped directly onto the refractometer If several drops can be squeezed out, drop them onto a small plate, mix them with a transfer pipette (Pasteur pipette) and put 2-3 drops of them onto the refractometer.

5. Close the lid of the refractometer and read the sugar content on the scale.

6. Repeat steps 4 and 5 several times and calculate an average from the readings. Between measurements, wipe the refractometer and the plate with a soft cloth, so that there are no more liquid residues from the last sample. lso make sure that there are no liquid residues in the transfer pipette, if necessary rinse with tap water in between and remove the water as well as possible.