Timothy & Sugars

by Lynda M. Vanden Elzen

Timothy Grass, Langley BC

Recently, we posted here about some of the many misconceptions and some general information about Alfalfa & Protein, and the article got a big response.  Alfalfa is not the only type of hay that is misunderstood – we receive calls from customers all the time who have been told that timothy hay is always low in sugar, or that it is “too rich” for their horses.  We have even heard of vets and equine nutritionists, supplement companies, forum threads and websites etc, telling horse owners to feed timothy hay to their laminitic ponies because it’s always low sugar or always low in calories.  Well, we’re here to tell you it is just not anywhere near that simple.  Feeding any kind of untested hay to sugar-sensitive horses is very risky.  We have done tests ourselves on timothy we didn’t end up buying because the NSC (Non Structural Carbohydrate) values were up to 24%, when sugar-sensitive horses should not consume an NSC of more than 10-12% depending on whose research you’re following.  Even regular hardworking horses with healthy sugar metabolisms should not consume hays with NSC values over 18%.  Please check out our Testing & Nutrition page for further testing guidelines provided by Shelagh Niblock, BSc.Ag., PAS.

No type of hay is always low sugar, or always high in protein, or always anything.  The only way to know the nutritional content of your hay is to test it.  Period.  You cannot tell by looking at it, smelling it, tasting it, by what cut it is, where it was grown, how that same hay tested last year, what time of day it was cut, whether your horses do or don’t like it, what colour it is, how coarse it is – the list goes on – and you still can’t tell.  Sorry.

On hay tests, sugar values show up as WSC (Water Soluble Carbohydrates), ESC (Ethanol Soluble Carbohydrates), Starch, NSC (Non Structural Carbohydrates, which can be calculated as WSC + Starch), and Fructans (WSC-ESC).  Here are some definitions of these terms from Dr. Juliet Getty, PhD:

Non-Structural Carbohydrates (NSC) —  the total amount of sugar, starch, and fructan. To obtain %NSC, add together %WSC (water soluble carbohydrates) + %Starch. If your horse needs to have a low sugar/low starch diet, the %NSC should be <12%.

Water-soluble carbohydrates (WSC) —  measures simple sugars and fructan levels. Simple sugars are digested in the foregut and raise insulin levels. Too much can lead to laminitis because of elevated blood insulin. Fructan, on the other hand, is digested in the hind gut. Too much can result in laminitis caused by endotoxins in the bloodstream.

Ethanol-soluble carbohydrates (ESC) —  a subset of WSC and gives you a better idea of the simple sugar level. WSC minus ESC provides a fair measurement of fructan levels.

Starch —  normally digested in the foregut down to individual glucose (blood sugar) molecules; therefore, it has a strong elevating effect on blood insulin levels.

There are some factors that can contribute to hay testing a certain way.  For example, because grasses accumulate sugars throughout the day in order to grow during the night without photosynthesis after the sun goes down, the sugars in the grass are lowest in the very early morning before the sun comes up.  If the grass hay is cut at this time, then the sugars will most likely be lower than they would have been if that same hay had been cut in the late afternoon, but you can only compare that one specific hay to itself.  You cannot generalize and say that all hay cut at 5am will be low sugar; likely that specific hay will be lower sugar than it would have been if it had been cut at 4pm.  But even that depends on other factors, including the overnight and daylight temperature, cloud cover, shady vs sunny areas of the field, and how stressed the grasses are due to things like weather, drought conditions – I think you see that it is not black and white.

From Kathryn A Watts, B.S. and N. Jerry Chatterton, PhD:

Sugars are the substrates for all plant growth, thus, they are critical to plant growth and development.  Sugars are produced by photosynthesis during daylight.  At night plants use energy from sugars formed by photosynthesis to grow.  Whenever the rates of photosynthesis exceed plant growth rates, carbohydrates accumulate.  At times, plant stresses decrease growth rates more than photosynthesis and carbohydrates accumulate.  Factors that contribute to plant stress include water and nutrient deficiencies, salty soils, as well as cool temperatures, especially those below 5°C.

There are some things you can tell by looking at hay: a coarser hay is probably higher fibre, for example.  You can look at a hay that is a mixture of grasses or grass and alfalfa and see the approximate percentage of each species that makes up the mixture.  Grasses that have been left to grow for a longer period of time will have more mature stalks and seed heads, where alfalfa hay that is post-bloom will contain purple flowers.  Usually, second cuts don’t grow for as long a period of time as first cuts, so they are softer (i.e. they contain less mature plants.) Plants that have gone to seed – so post-bloom alfalfa and grass hays with seed heads – will tend to be lower in protein than they would have been if they had been cut before the seed heads or flowers appeared, and grasses in the active heading stage will probably be higher in sugars.  Unfortunately, none of these observations can tell us anything about sugar levels or protein levels as compared to other hays.

Kathryn A. Watts, B.S., and N. Jerry Chatterton Ph.D support the idea that rules of thumb with regard to sugar levels in grass don’t always work:

In general, mature plants that are high in fiber are low in carbohydrates.  However, environmental conditions have a very large impact on carbohydrate content.  Under some circumstances, environmental factors may be more important than stage of plant growth.  Very young, rapidly growing grass under ideal conditions are often lower in carbohydrates than at later stages of vegetative growth.  Conditions in the spring and in the fall often favor carbohydrate accumulation, regardless of the stage of plant growth.  A frost, or a hot, dry wind, may cause rapid changes in carbohydrate concentrations within a very short time.  Climate and plant species are so important in determining carbohydrate levels of forages that it is difficult to generalize about carbohydrate concentrations, especially in forages from various parts of the country or world.  Simple statements such as “avoid grazing lush grass” do not guarantee low carbohydrate levels.  Certainly, there are times when ‘lush’ grass is high in carbohydrate.  Instances when grass plants are cool temperature stressed, or when in the heading stage, are often troublesome times and should be of concern to care takers of sugar intolerant equines.

We see many hays here that look like they’ll probably be lower sugar – they have more alfalfa than grass – and then the test comes back and we find we were wrong.  It happens all the time.  We had a 2nd cut orchard/alfalfa mix in 2014 that was probably 50% alfalfa, soft, green, and lovely, with few seed heads.  The NSC was almost 22%.  We also see significantly different tests from the same farmer’s field depending on the year.  The only way to know is to test.

Timothy hay in particular tends to be quite variable in protein and sugar content.  Why is that?  Well, first let’s define what timothy is, because we find many horse owners are unable to distinguish between timothy and orchard grass, or other grass hays.

From the United States Department of Agriculture Natural Resources Conservation Service Plants Guide:

Timothy is a relatively short-lived, cool-season, introduced perennial grass that grows in stools or clumps. It has a shallow, compact, and fibrous root system. It grows in erect culms 50 to 100 cm (20 to 40 in) tall. Leaves vary in length from a few inches to more than a foot and are about 0.6 cm (0.25 in) wide, narrowing gently toward the tip.

Cool season grasses like timothy, orchard grass, and brome are able to grow in more northern climates because they are better at storing sugars than warm season grasses like those that grow in the southern United States.  Great for the grass – not so great for overweight sedentary horses.  In contrast, grass hays tend to be lower in digestible energy than legume hays like alfalfa, so it becomes a balance between providing adequate protein and minerals while ensuring the sugar levels and caloric density are not too high.




Orchard Grass

grass-smooth brome

Smooth Brome Grass


Meadow Brome Grass

The best way to tell the difference between timothy, orchard grass, and brome grass is by its seed heads.  Here are some photos, from the Ontario Ministry of Agriculture, Food, and Rural Affairs, of the various types of seed heads for your reference (left).

In this article, we have singled out timothy because it is the grass hay about which the most myths and misconceptions are circulated, but all cool season grasses are similar in that they store fructans and are very good at storing sugars in general.  This is what enables them to survive in colder climates.  It also means that when those grasses are stressed, they hay we make from them can vary widely in sugar levels.  That said, in our experience, having tested hundreds of stacks of hay, timothy seems to vary more in sugar levels than the other grass hays we test.  It turns out that timothy has a unique carbohydrate storage system.

According to the Washington State University Extension Drought Advisory:

Timothy is unique among grasses in that during the autumn it develops a corm, which is a bulb-like structure, from an elongated internode. Water soluble carbohydrates, mainly fructans (chains of fructose sugars with a terminal glucose sugar), fill the corm until after the flowering stage in the spring. Fructan concentration then declines in the seedhead stem as starch content increases in the seedheads. Very little fructan is stored in the seeds at crop maturity, since starch is the primary storage carbohydrate in the seed. Highest fructan concentrations are found in stem bases (the region from soil surface to approximately 3″ above the ground) and the corms. Fructans molecules are stored in the vacuole of cells and vary in length and size, depending on the grass species. Fructans are produced from sucrose (common table sugar) during photosynthesis and can be created any time of the day or night. Timothy fructan molecules are larger than those in other cool-season grasses and actually more resemble those of onions.

To illustrate how much timothy can vary, we created the following infographic to display at our trade show and horse show booths as a conversation starter with the horse people we meet. You can click on it to open a larger version if this one is too small:

Test Comparisons - 1st cut Timothy (11x17)You’ll find that the test on the left was an excellent batch of timothy, but the one on the right contained a sugar level that is unsafe for the majority of horses, and has woefully inadequate protein levels as well.  These two hays looked very similar and were grown in the same area during the same year and cut at approximately the same time.  Feeding the hay from the test on the right to a sugar-sensitive horse every day would be like feeding a diet of mars bars and caramel corn to a diabetic person.  Timothy is not always or even often low sugar.  Sometimes it is.  But the only way to know if the timothy you are feeding is low sugar is to test it.  If somebody tells you timothy is always low sugar hay, they are wrong.  

All of that said, we must remember that we cannot generalize that all horses should eat a low sugar/carbohydrate diet with an NSC under 10-12%.  Shelagh Niblock, BSc.Ag., PAS and Senior Nutritionist at Hi Pro Feeds points out that where horses in the past worked for a living and were rarely obese, and did not live into old age after their functional lives had ceased, our 21st century horses tend to be overfed, underworked, and as a result, are suffering from metabolic issues they would not have 100 years ago.  For these horses, and for those with other disease conditions that are exacerbated by excess sugar, low starch diets are crucial.  But, for horses who still do work hard for a living, carbohydrates are an important energy source.  According to Shelagh:

Both starch and sugar are important energy sources for the high performance equine athlete and, when fed appropriately, they are not dangerous or “bad” for your horse, assuming that he is otherwise healthy. Carbohydrates such as starch should be fed in small amounts per meal so that the starch is digested before it moves out of the foregut. Excessive starch fermentation in the hindgut can cause deleterious changes in hindgut bacterial populations, potentially resulting in health problems such as gas colic, chronic and/or acute laminitic episodes, and hindgut ulcers, to name a few. Small meals ensure that starch is more likely to be digested in the small intestine and that fluctuations in blood glucose as a result of starch digestion are smaller and more efficiently regulated by the insulin secreted by the pancreas.

In conclusion, the take home message here is that we simply cannot generalize that all timothy or other grass hay is low sugar, or that all horses will thrive on a low sugar diet.  We can’t generalize at all; every stack of hay and every horse is an individual, and must be treated as such.  The factors that influence both the sugar levels in grass hays and the carbohydrate requirements of horses are complex.  We would prefer to be able to lay out a list of cut and dry feeding guidelines for all horse owners to live by – it would make our jobs easier and our horses happier!  Unfortunately, it just isn’t that simple.



“United States Department of Agriculture Natural Resources Conservation Service Plants Guide” (http://plants.usda.gov/plantguide/pdf/pg_phpr3.pdf)

“Managing a Horse with Laminitis on Grass Pastures” – Ann Swinker, Penn State University Extension Equine Specialist (http://extension.psu.edu/animals/equine/news/2013/managing-a-horse-with-laminitis-on-grass-pastures)
“Factsheet: Pasture Grasses Identified” – Ontario Ministry of Agriculture, Food, and Rural Affairs (http://www.omafra.gov.on.ca/english/livestock/beef/facts/06-095.htm)

“Drought Advisory” – Washington State University Extension (http://cru.cahe.wsu.edu/CEPublications/em4919e/em4919e.pdf)

“How to Interpret Your Hay Analysis Report: the Basics” – Dr. Juliet Getty, PhD (http://gettyequinenutrition.biz/Library/Howtointerpretyourhayanalysisreport.htm)

“A Review of Factors Affecting Carbohydrate Levels in Forage” – Kathryn A. Watts, B.S., N. Jerry Chatterton, PhD (http://www.safergrass.org/pdf/AAEP.pdf)

“Low Starch Diets: Manage Carbohydrates to Your Horse’s Best Advantage” – Shelagh Niblock BSc.Ag., PAS (https://www.horsejournals.com/low-starch-diets-manage-carbohydrates-your-horses-best-advantage)


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