Decomplexicating Equine Nutrition Part 02 of 12 – The Basics of Sugar, Fat and Proteins

Welcome back! In the last article, I reviewed 3 types of sugar important to horses. They were glucose, which is a single molecule of sugar (monosaccharide), starch, which is a chain of glucose molecules linked together (polysaccharide) in a way the horse can digest using enzymes, and finally cellulose which is the same chain of glucose molecules linked together in a different way so that the horse cannot digest it but the gut microbes can.

Remember also that every glucose molecule is made up of the elements C H and O (carbon, hydrogen and oxygen). Do you know what elements makeup fat?


C H and O. Yes the same atoms are used to make fat but they are put together differently. Is it possible that a molecule of glucose could become a molecule of fat? Definitely. In fact every time there is an excess molecule of glucose, the body converts it into a fatty acid or a triglyceride (a type of fat) and stores it as fat on the body.

How about proteins? They are made of amino acids chained together like letters that make words. What elements are in amino acids? If you say C H and O you would be almost correct. Added to these is the element nitrogen (N) and you have an amino acid. Of the 20 amino acids, there are 2 that also have a sulfur element. Can an amino acid become a sugar? Absolutely through a process called gluconeogenesis.

Basically, you, me and our horses are mostly made of solid carbon and 2 gasses – hydrogen and oxygen. Have you ever burned white table sugar? If you have then the gasses are evaporated leaving you with a solid black substance which is the carbon – and a ruined pan. The concept here is that the body is simply chemistry with only a few ingredients and how those ingredients are put together will make the variety of things needed to make you and your horses operate. So everything in us has the ability to become something else – like a horse trainer could become a stall mucker if needed.

I really want to make feeding a horse something we all can understand because once understood, you will never feed your horse incorrectly ever again. To do so, this concept needs to be fully understood. Everything in the body is a variation of the basic group of C H and O. These molecules are so small that no one has ever photographed them. Think of it this way. A cell is very small but we can see them under a microscope. Within a cell are between 1 and 3 billion proteins and each protein is made up of hundreds, thousands and even tens of thousands of amino acids. And every amino acid is made up of C H O and N elements. The body has the ability to break apart the molecules and reform them into something completely different according to its needs.

We need an example from the real life of a horse. I’ll use Buster the pony. He is out grazing on grass all summer which is softened by chewing, gastric acid, enzymes and gut bacteria. The first to come out is the starch which is how the plant stores energy. Also coming out are the plant proteins which are broken into smaller peptides (like syllables of words) and the individual amino acids. But the cellulose is not digested until it reaches the cecum and colon and the bacteria there break apart the bonds between the glucose, upside-down glucose, molecules. Then the bacteria turn these glucose molecules into short-chain fatty acids. These are what the horse absorbs and uses for energy. In essence, he is eating a high-fat diet. This is very important to understand especially when I discuss the 2 basic fuels of the body – glucose and fats/ketones.

A meal of grass provides horses with a lot of fat, some sugar and a few amino acids. All of these are small enough to cross the intact gut membrane and are sent throughout the body for use. Glucose can power some of the functions but where it first goes is to the liver, muscles and brain where it is stored as glycogen. This is where they get quick energy for bursts of speed. It is similar to the starch of plants but it’s got a different name in animals (glycogen). Any excess is transported by the hormone insulin to fat cells where it triggers the cell to make more fat.

Glucose in the form of plant starch becomes more abundant in summer and autumn before winter when food becomes scarce. The purpose of finding sugar-laden foods is to create the fuel storage of fat so we have something to use when there is no food. Horses eat as much grass as possible during the summer and fall and are supposed to gain fat weight doing this. Most importantly, as long as there is glucose available, insulin is used to get glucose into cells and to store excess glucose as fat also preventing the conversion of stored fat into the alternative fuel called ketones. When food becomes very scarce and body fat is gone, the proteins of the muscles are converted into glucose to prevent the horse from dying.

The fattening and thinning of horses and humans are millions of years old and it works. However when there is a constant supply of glucose throughout the year, fat continues to be formed causing obesity. And glucose is available to humans and horses every day throughout the year in the form of fruits and grains. The excess glucose overworks insulin and the power generators within the cell that are called mitochondria. At some point, the job of insulin and the ability of fuel conversion into energy is compromised and is referred to as insulin resistance.

But it is actually much worse. Remember the good gut bacteria happily digesting cellulose? They are replaced with bacteria happy to live on a high carbohydrate diet. Now the fiber cellulose is not effectively digested and the health of the gut becomes compromised. Some of the effects of this include wet feces or squirts, poor absorption of protein and a horse that becomes hungry all the time.

Why is the horse hungry? Because of the abundance of glucose, energy needs are not met. The system is overworked because it was never designed to work this way every day. They need time off from the fuel glucose. Horses need fat to become satiated and function efficiently during the lean months and without good gut bacteria, the fat isn’t made. This leads to the next article.

The Equine Practice Inc, mud trucks
At this point, your brain may feel like mud trucks that are frozen and stuck. Just reread this blog and do it again because as you understand the concepts of feeding the horse, everything will start to make sense.

The take-home messages:

1) Carbohydrates, fats and proteins are built on the foundation of a simple molecule made of carbon, hydrogen and oxygen atoms. How this molecule is put together into chains or whether a nitrogen or sulfur atom is added will determine what it is and what it does. Enormous combinations of these molecules provide the variety of materials needed to make the body take form, function and survive. These molecules can transform between these three forms (sugar, fat, protein) to meet the needs of the horse. The most important point is that the horse has evolved to take in a limited form of food to make all of this work properly. Adding foods that have not come with this evolution alters the process leading to imbalances and disease. Anything added to this diet in the past 4000 years when they were domesticated by humans is considered new to a horse and its 55,000,000 years old (55 million) gut microbes.

2) Continuous feeding of glucose-laden foods in the form of plant starch (grains), sugar cubes, carrots and apples overworks the insulin system, the mitochondria energy generator, causes increased storage of fat and prevents the loss of this fat. This imbalance in the time-tested system of the horse leads to disease in all systems of the horse including protein deficiency, muscle loss, lameness, hormonal disruptions, neurological syndromes and autoimmune diseases.

Don’t worry if you feel a little overwhelmed especially when some of this is so different from what you thought you knew. Just keep asking this: Is what you are doing now working? If not, stay tuned. More next week on gut microbes and the mighty mitochondria.

Be sure to read all the comments from the original post below before you go.

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  1. Thank you for your great articles. Do you prefer certain grasses and certain grass hay? My mare likes 2nd cut orchard grass. Do you suggest alfafa cubes when a horse can’t chew hay in winter? ( my gelding’s teeth were floated with an electric tool at about age 29, biggest mistake ever! ) He is getting 9 lbs.of senior feed every day at 2 hr intervals via an auto feeder because his teeth were ruined. It can only dispense dry pellets and i worry grass pellets are too hard to chew. I do feed some hay cubes and chopped hay in am and pm for long stem forage. Alfafa is only packaged type available which i dont like for horses. For years i fed mostly hay and pasture so it was very affordable. Now it’s so expensive, it’s hurting me financially. Any suggestions would be appreciated. Thank you.

  2. We have Padock Paradise, “track system” setup for our six , two donkeys, mule and 3 horse. I put small piles “a flake or two throughout our quarter mile track. The donkeys were over wieght when we first got them and now a year later they both look great. The movement that this apraoch creats made all the difference for use. Best wishes for you and yours.

  3. I feed no grains fruits, or any such sugar laden foods. The hay is tested at Equi-Analytical before purchasing to insure low starch and sugar, 10% or less. Typically these hays rate very low in nutrition or have faults such as low phosphorus or high iron. My nutritionist checks what needs to be added for a horse to be at balanced health coupled with weight loss and suggests supplements for me to add to her feed. I mix those supplements with hay cubes and a cup of alfalfa pellets, both soaked. For some reason I can’t seem to find a hay which helps her to drop weight. I look for prairie hay, bermuda, and teff. We live in Kansas.

    My mare is out 24/7 on 1 acre of dormant bermuda with some cool season grasses interspersed that I can’t seem to get rid of. She also eats from a 1.25″ hole slow feeder net 24/7. Truthfully tho, in order for her to drop weight, I let the net go empty often, thinking she still has dormant pasture on which to graze. Currently she’s fed 25-28 pounds of purchased hay, unless the cold is so bitter that I definitely don’t want her net to go empty. No blanket either and not stalled, but has a shelter with an automatic waterer.

    The bulk of her hay is purchased. My pasture tho, is sprayed regularly with glyphosate, 2,4,D, and for foxtail I use Prowl H2O, a pre-emergent. I’m almost positive none of this is good for her, but I want you to know all the information I can muster up.

    She is fifteen this year and I’ve spent bunches of bucks for the last 5-7 years attempting to help her lose weight without restricting hay. She looks fair now 14.3 and 1148#. Too much in my opinion. Her ribs are easily felt, but because of winter coat, I’m unsure if they are visible. She could probably stand to lose another 150#. When the pasture greens up, I’ll most likely need to take her off turnout and return her to her 30×60 dry lot to keep her off the grass.

    At my age, 76, she is not ridden much. I’ve always thought that’s the ingredient missing in her care. She was born on my place. She has been a single horse since her dam died in 2011. Hubby doesn’t want me to incur another expense to add a buddy for her. Limited income you know.

    I can’t figure out why this is so hard and unsuccessful.. 😟

    1. Thank you for such a complete description! So this is what I see: she has access to hay and pasture with some supplements mixed after analysis. I would like for you to discuss this with your vet because I see some holes in it.

      First – glyphosate damages the energy production cycle of bacteria. While basically OK for human cells, it damages and destroys the good gut microbes which digest cellulose turning that into the efficient fuel of fat. Instead your horse is making more glucose from what is being fed even though the starch content is measured low. I would like to know how the cellulose is being digested by the challenged gut bacteria (glyphosate) and whether the glucose molecules of cellulose are being made available for transport into the horse. This would lead to insulin resistance, mitochondrial overload and increased fat storage and prevention of fat mobilization.

      Second – where is the protein? If you did the calculations would there be between 0.5 and 1.0 g per lb of protein being ingested? Is is from multiple sources to provide a variety of amino acids? Is the gut inflamed or on any medication that is preventing absorption of these proteins? All of these things will be covered in future articles but 1 observation here. Horses on a high protein diet (0.75 g/lb BW) along with reduction in gut inflammation (all grass diet) lose their pot belly, increase their top line and no longer are constantly hungry (“Hoovers”). For more info go to the blog on this site:

      1. How would a vet check for cellulose digestion? Should I take in a sample of manure? This past fall she tested negative for insulin resistance. I suppose I should discontinue spraying glyphosate unless maybe spot spraying for grassy undesirable weeds. But what of the 2,4,D and Prowl H2O (Pendimethalin)?
        Protein: the nutritionist has recently added three different protein supplements for as many Amino acid sources as possible to her daily food. I believe she wants her protein to be at or above .80.
        I do think she is much better than earlier this year. Her belly is better but still when walking away from me the belly is fairly prominent in swinging side to side.
        Your latest on gut microbes is highly interesting to me and I wonder if that is part of her problem and how to remedy that.

        I find your articles wonderfully informative! Maybe through more suggestions of yours I can figure out how to get my mare in good shape.