Unit 13 is the final unit of the Advanced Equine Nutrition course. The complete text is here, but a video and quiz questions are available with The Horse’s Advocate membership. You can also purchase them separately. Note: Passing the Basic Equine Nutrition Course is required before starting the Advanced Course.

Feeding horses is very simple when considering their evolutionary development and how foods are digested and used.

Life is created and maintained by extracting fuels chemically bound in food. Every living thing evolved to consume specific food types and developed species-specific digestive systems to extract those fuels. Horses are obligate herbivores. Unlike ruminants (cattle and other even-toed ungulates), horses (an odd-toed ungulate) cannot eat lignin (woody cellulose), so they will only eat ground plants unless food becomes scarce.

Ground plants contain starch and free sugars, which are the primary fuels used by all animals, including horses. These plants also contain amino acids, the building blocks of protein, used in every living thing for structures and life-maintaining processes.

Cellulose is the world’s most common polymer (chemicals with many repeating units), found in every ground plant. It gives plants their structure. Through hindgut fermentation, horses break down cellulose into short-chain fatty acids, one of the fuels needed for energy production in all animals.

All life follows a simple survival plan, and horses are no exception. They find food, harvest it, digest it, and send the fuels derived from digestion to every cell. Then, the fuel is converted from chemical to electrical energy, which creates movement within cells and throughout the body, maintaining life. When used up, energy is removed from the body as waste, which plants use to continue the life balance between plants and animals.

This course focused on the flow of energy from the chemicals found in food, the distribution and factors controlling the fuels derived from food, and the various processes involved in using fuels to develop energy in mammals. Anything that inhibits or interrupts this grand scheme of nature will lead to disease and the eventual loss of life (entropy).

Let’s review the units.

Unit 1 – Feeding Horses: Beyond the Basics

This unit introduced the Advanced Equine Nutrition Course. The thrust of this unit’s message was that learning this material may be difficult for you, but with effort, it can be understood and learned. The strength through knowledge approach allows horse owners to stand as advocates for horses against the pushback that is common from horse owners, barn managers, and constant marketing messages.

Unit 2 – The Science Of Nutrition

This unit looks at what makes scientific studies valid. Unfortunately, data can lie when manipulated, so horse owners need to know the tricks used in research against horses.

The first trick is in selection bias, where subjects used are selected to affect the result. An example would be gender, such as using only geldings, or breed, such as using only Thoroughbreds.

The next trick is using too few subjects in a study, called under-powering. Adding subjects costs money, which equine research needs more of. Not only are horses expensive to purchase and maintain, but there is also the cost of materials for the study and data processing. Adding to under-powering is the effect of using a horse in several studies simultaneously.

Finally, an argument can be made that research is driven by agenda-driven marketing, bypassing what nature built over millions of years. In other words, is research helping horses, or is it slowly causing several ill effects over the last few decades? Were horses better off before equine research became popular?

Unit 3 – Energy Flux: The Flow Of All Life

The First Law of Thermodynamics states that calories in (consumed) equal calories out (expended), which works well for non-biologic systems such as money. However, other factors affect both sides of this equation when considering the numerous biological processes affected by the prevalence of nutrients, stress, and disease. 

As a horse owner, your role is not just important; it’s crucial and empowering. You are the one who “adjusts the dials” when feeding, considering the individual variations between horses and ensuring their well-being.

Entropy is the word used to describe the Third Law of Thermodynamics, which states that any living order requires energy to maintain it. Without energy, all things descend into complete chaos or nothingness, where atoms no longer have the power to maintain form. The energy comes from stored fuels within the food the horse consumes and must reach every cell at every moment of life.

Air, water, glucose (and other sugars), fat (fatty acids), and amino acids (proteins) are the fuel sources required for life. Horses either make these fuels (water, sugar, fat, non-essential and conditionally essential amino acids) or consume them (air, water, sugar, essential amino acids).

Factors affecting the energy balance equation can change in the blink of an eye, and constant adjustments are necessary to adapt. Vigilance and attention are crucial to preventing problems when some fuels are consumed in excess, causing the body to struggle to maintain a balanced equation. These problems include inflammation, obesity, protein deficiencies, and poor metabolic efficiency (Equine Metabolic Syndrome).

Organs’ varied requirements further drive energy balance, with the brain requiring more glucose than any other organ. Eating foods that increase or decrease any nutrient will alter the overall energy balance, requiring a metabolic adjustment by the horse. If continuous, over time, these adjustments cause the horse to develop disease and poor body conditions.

Unit 4 – Feeding Horses: Energy In

Energy is the ability to do work measured in calories or joules. One gram of protein or carbohydrate releases four calories, while one gram of fat releases nine calories.

The basal metabolic rate (BMR) is the energy required to keep the horse alive. The horse must store more energy to allow for sudden increases in energy (flight or fight), chronic increases in needs (sport, training), and epigenetic or seasonal changes. Various rules provide a starting point, but individual adjustments consider the variations between horses, emphasizing your significant role in your horse’s care.

Measurements and recorded observations (data) help to make individual decisions when feeding a horse. Insidious changes become evident when compared with your data entries. Develop an eye for the body condition score (BCS) and the top line score (TLS). Look for changes over time. Physically back up, observe the horse’s demeanor, and include this in the record. Recording anything else you feel necessary, such as changes in weather, sports level, and barn personnel, is essential because this will help in future observations.

Remember, you can only control the things that are within your control (e.g., food, environment). Don’t worry about the things you can’t control (e.g., the breed, weather). Avoid gimmicks and slick marketing. Know that you are not just feeding the horse but also feeding the gut bacteria, and they are also feeding your horse. Do the best you can with what you have and where you live. Keep “adjusting the dials” for the individual.

Unit 5 – DNA and Protein Synthesis

With every cell having billions of proteins and every horse having trillions of cells, it’s truly a marvel how all horses have similar features passed on to their offspring. DNA, often referred to as the ‘magic’ behind this similarity, is the topic of this chapter.

DNA is the blueprint for every living thing on this planet and is shared. Only 2% of DNA makes the proteins in a horse. The other 98% do other things that still need to be clarified to researchers. The horse (and any animal) creates all proteins in two steps: 1) through transcription (copying sections of DNA code) and 2) through translation (using that snippet of code stored as RNA). Defects in these processes can cause problems that are either repaired or become permanent. Several factors besides these defects can also cause problems, the most common being a lack of materials (amino acids) to build the proteins.

Mutations of the DNA change the code forever. However, epigenetics determines which DNA sequences can be expressed permanently (and which are NOT allowed), so we have horses, different breeds, and different looks within breeds. Epigenetics provides for adaptation to the environment and can alter the transcribed code. This change doesn’t alter the original DNA but passes on to all future cells using this adapted code. It is why individuals are different and why most diets work differently in other horses. Epigenetic changes can also occur in the microorganisms living in and on the horse. When too many epigenetic changes occur, illness and death may happen, or, conversely, the horse may thrive. “Adjusting the dials” is critical when caring for horses:

• Adjusting the amount and type of food.
• Eliminating stress.
• Observing what the individual requires rather than applying a one-size-fits-all approach.

Unit 6 – Protein: An Essential Nutrient

Protein, specifically amino acids, is the most crucial nutrient required for all horses. It should be the first consideration in a horse feeding program behind air and water.

There are three groups of amino acids: essential, conditional, and non-essential. The essential amino acids come to the horse in natural and manufactured forms. Little research is available on horse amino acid requirements, but what is known is to put as much of the amino acids available from high-quality sources into the horse as possible and trust the horse will use them as instructed. In other words, remove the limiting step in protein synthesis: lack of amino acids. Amino acids are the building blocks of proteins. Protein synthesis in horses, the process of making proteins, is crucial for the body’s growth, repair, and maintenance. Therefore, ensuring your horse’s diet is rich in essential amino acids is vital to their health and well-being.

Feeding pasture and hay with high quantities of sugar but equal protein to a condensed, high-quality protein source will also increase the total calories consumed. Therefore, feeding only forage to provide the daily requirement of all essential amino acids drives an increase in calorie consumption, leading to obesity and metabolic disease when exercise is limited. The limited grasses and legumes in pasture and hay are also limited in their amino acid profiles; the result is specific amino acid deficiencies.

Excess and recycled protein in the diet converts into glucose or ketones, and the freed nitrogen becomes ammonia, which is converted into urea and eliminated in the urine.

“Catabolic crisis” describes starvation caused by insufficient or excessive food intake, which converts amino acids into glucose. Muscle loss (sarcopenia) and weakening and loss of other protein structures are evident in these two paradoxical cases.

In humans (I assume in horses, too, but I need clarification on the percent), the free amino acid pool supplies 15% of daily glucose production through gluconeogenesis, so these amino acids are lost. The pool recycles the remaining free amino acids into other new proteins. Additionally, protein is lost with hoof trimming and hair clipping. These protein losses require replacement through food consumption.

Proteins can also act as signaling molecules, indicating that a process can move forward (e.g., leucine, mTOR, and muscle growth).

Unit 7 – Fat And Carbohydrate: Not So Essential Nutrients

Fats and carbohydrates are the primary fuels that power horses’ cells. Horses can produce most of their fats using the hindgut bacteria to ferment cellulose. The enzymatic breakdown of plant starch derives glucose. Other carbohydrates in the form of free sugars are also in plants, with higher levels in the young, growing plants of spring and in autumn for the winter-resistant varieties.

Free glucose in the blood damages proteins through glycation. Binding glucose to insulin protects the horse from this. Most cells require insulin to get glucose into the cell, but there are some instances in exercised muscles and some locations in the brain that do not need insulin for glucose uptake.

Excess glucose becomes glycogen stored in muscles and the liver or is converted into a free fatty acid and stored as body, visceral, or organ fat. Fat can flow freely into cells and is stored in fat droplets with attached mitochondria, but when these droplets are full, fat is not allowed into the cell but is added to the body. When food becomes scarce in winter, stored fuel mobilizes through lipolysis, delivering fat for cell use. When food doesn’t become scarce, as in feeding the same food every day of the year, stored fuel increases as body fat through lipogenesis.

Continuous excess carbohydrate intake leads to systemic insulin resistance with the following secondary results:

• decreases glucose availability to the brain.
• increases the conversion of amino acids into glucose (gluconeogenesis, catabolic crisis).
• increases lipogenesis, and leads to obesity.
• increases cell oxidation, leads to cell inflammation, and decreases metabolic efficiency.

Unit 8 – Cell Metabolism: Energy Used, Stored, And Removed

The Randel Cycle measures the concentrations of glucose and triglycerides inside and outside the cell. Based on the relative differences between the two, it mediates the processes that move these substrates into the cell. It does this throughout every moment of life and creates momentary insulin resistance to keep glucose outside the cell when enough is inside.

There are three situations of substrate availability:

• A seasonally high-sugar diet
• A seasonally low-sugar diet
• A continuously high-sugar diet

When a high-sugar diet is available throughout the year, the mitochondria become stuck over time, leading to the cell’s demise through increased cell inflammation and, finally, apoptosis (programmed cell death). 

Insulin resistance occurs typically as a moment-by-moment event that lowers, but doesn’t eliminate, glucose’s ability to enter the cell. However, with continuous excess sugar in the diet, IR becomes systemic and constant, and limited sugar enters the body’s cells. The fine-tuning control of the Randel Cycle, which creates a balance between using fat and glucose for fuel, becomes a more permanent shutdown of glucose uptake into the cell, decreasing fat availability for fuel. The overall effect is a slowdown in cell metabolism and the eventual death of the cell. With enough cell death, disease and breakdowns occur in the horse.

Unit 9 – Lactate: The Universal Fuel

Recent discoveries show that lactate is derived from glucose at all levels of oxygen availability (aerobic) and not just in a low-oxygen state (anaerobic). This production helps to maintain a basic pH within the cell and is, therefore, not a cause of acid build-up, debunking the notion that lactic acidosis causes muscle pain.

Lactate is the primary fuel source of all cells: glucose stores lactate, glycogen stores glucose, and fat stores glucose. Lactate is formed chiefly in the enterocytes before excess glucose can enter the body bound to insulin. The prevalence of lactate preserves the remaining glucose for future use.

With abundant dietary glucose, lactate increases within the cell through glycolysis, increasing ADP, signaling lactate uptake by the mitochondria for ATP production, and preventing fatty acid uptake there. Excess lactate can leave the cell and be shared with other cells or returned to the liver using the Cori Cycle to produce glucose. If excess lactate remains in the cell due to decreased energy flux, it may trigger unwanted cell division, also known as cancer.

Fast-twitch Type II muscle fibers are more concentrated in the neck, shoulders, and forearms, while slow-twitch Type I muscle fibers are more concentrated in the hips, rump, and hind limbs. They can share lactate using the cell-cell lactate shuttle, forming an “energy grid” that also includes signaling between mitochondria of all muscle fibers.

Insulin resistance (IR) and insulin sensitivity (IS) rapidly interchange in the healthy cell. However, increased glycolysis from excess dietary glucose increases cell inflammation, causing slower, inefficient cell metabolism and resistance in energy flux. IR predominates and is measured in the blood, which is the hallmark of EMS but is also evidence of a long-standing problem.

Lactate is neurons’ primary fuel, and when lactate is limited (starvation), ketones are the secondary fuel, using the shared MCT transport mechanism. High-sugar diets reduce glucose availability in the brain through IR and blood-brain membrane inflammation, reducing lactate availability for neurons (and limited ketone availability due to insulin-caused decreased lipolysis), affecting cognitive function.

Exercise increases lactate production by releasing glucose from glycogen and increasing glycolysis. It also increases mitochondrial density, allowing for the consumption of extra lactate. Exercise also creates new muscle fibers, dense mitochondria, more MCT channels, and more enzymes to metabolize lactate. 

Increased lactate inhibits ghrelin, thus reducing appetite and caloric intake. This action, combined with rest, allows for the clean-up of excess cellular ROS (free radicals).

Unit 10 – Fructose: The Master Fuel For Survival

Fructose is a sugar that attracts animals to eat sweet fruit to help spread plant seeds. It does this by appealing to the sweetness and creating moderate gastric irritation by altering the microbiome, ensuring the passage of any eaten seeds.

In return, the animal eating fructose prepares for the winter by:

• adding body fat (warmth).
• slightly increasing blood pressure (ensuring peripheral blood when dehydrated).
• creating low-grade inflammation (to fight off infections in a low-energy state).
• driving foraging behaviors (to eat more at the expense of others or to migrate).
• decrease cellular energy production (reduce the basal metabolic rate to reduce the need for food in winter and preserve body fat).

The seasonal availability of fructose for horses (and all animals) allows for the temporary effects of preparing for winter harshness. But when fructose is unavailable, the horse will reverse all the ill effects of fructose metabolism. By spring, body fat is reduced along with the normalization of blood pressure, inflammation, foraging behaviors, and the basal metabolic rate. Horses also exhibit mating behavior, and young horses grow and play.

Two factors are upsetting the ebb and flow of fructose availability. The first is feeding foods high in fructose year-round. It comes from feeding the preserved, rapidly growing summer pastures as hay to horses in the middle of winter. The second is triggering the Polyol Pathway, converting glucose into fructose. There are four separate triggers:

1. Eating high glycemic foods such as starch found in grains and hay.
2. Becoming dehydrated when eating salted foods before drinking water or having decreased water availability.
3. Eating umami foods, including yeasts and foods high in glutamate.
4. Living in a low oxygen environment, such as being stabled without exercise.

With continuous access to fructose through food or converting glucose (starch) to fructose, the horse gains unwanted body fat and becomes metabolically unhealthy. Fructose is the root cause of Equine Metabolic Syndrome, which manifests as excess body fat and dysfunctional metabolic processes, such as insulin resistance. It also leads to hunger, craving, other aggressive eating behaviors, a poor work ethic, and breakdowns in soundness. 

We need to find a better test to indicate the start of EMS long before insulin resistance develops. While measuring blood uric acid levels seems a likely place to start, so does identifying altered behavior and increased body fat, both of which are free ways to identify EMS.

Unit 11 – The Addiction Of Sugar In Horses

This chapter delves into the known addictive behaviors of sugar in humans, which are akin to those associated with heroin and alcohol. The consequence of excess sugar or alcohol is fatty liver disease. Studies have shown alcohol itself does not cause liver disease, but the conversion of glucose into fructose (Polyol Pathway) does. The Polyol Pathway is a metabolic process that converts glucose into fructose. It’s the behavior driven by fructose that enforces the addiction that alcohol is trying to quell. In horses, sedatives, tranquilizers, and behavioral supplements offer a similar solution to the addictive behavior of fructose metabolism.

Fructose metabolism is the process by which the body breaks down and uses fructose for energy. Uric acid is the end-product of this process and is usually eliminated through the urine bound to estrogen or by enzyme disposal. However, when chronic, excess uric acid drives several human mental disturbances (ADHD, bipolar disorder, aggression, impulsiveness) due to decreased glucose availability in the brain. Foraging behavior, enabled by uric acid, consists of many behaviors meant to improve survival in lean times, including migration and fighting others for food. 

Increased fructose production through the Polyol Pathway in the brain may be the root cause of Alzheimer’s in humans. Its negative effect on cell energy, by limiting lactate production, eventually causes neuronal death. While cognitive loss in horses is undetermined, there is evidence of decreased glucose availability in specific brain regions, possibly leading to other known disorders, such as PPID.

Finally, horses raised in the last 50 years have had increased access to fructose year-round through unlimited hay access and the factors triggering the Polyol Pathway that increase fructose production within the horse. The increased and constant availability of fructose has led to conditions and diseases unknown to horses raised before their availability. Understanding the impact of fructose metabolism on horse health is crucial, and by gaining this knowledge, you can effectively manage and prevent these conditions, feeling informed and knowledgeable in your role as a horse owner.

Unit 12 – Stress: Its Impact On Horses

Stress comes in two forms: acute and chronic.

• Acute stress helps horses survive an attack and promotes the creation of abundant energy through increased blood glucose, lipolysis, and gluconeogenesis.
• Chronic stress helps horses survive long-term threats like winter and promotes energy storage through lipogenesis, insulin resistance, and reduced metabolism. 

Both forms of stress are reversible when the danger is removed, and time allows for neutralizing the associated stress hormones.

Hormesis occurs when life applies everyday stress from the environment, such as the body weight caused by gravity. It becomes a “set point” that the body works at maintaining, such as sleeping. Allostasis occurs when the body changes the hormesis set point in response to chronic stress. It is the body’s acclimation process to adapt; for example, increased bone density to support increased body mass.

Oxidative stress is a byproduct of the cell’s metabolic processes, particularly within the mitochondria. Free radicals are the unstable forms of environmental elements (atoms), and when they occur inside the body, they are called Reactive Oxygen Species (ROS). ROS can be signaling compounds at low levels, but at high levels, they add to the body’s overall stress. Removal can be achieved with time or by reducing or eliminating their cause. At low levels, ROS serves several purposes, like killing invading bacteria. However, they add to the body’s total stress at high and chronic levels, causing allostasis and eventually adding to the EMS of horses.

Increased oxidative stress results in autophagy (the cell digesting internally damaged organelles) and apoptosis (programmed cell death). While these processes occur constantly, excessive use leads to illness and even death of the whole body. Adding “anti-oxidant” supplements may counter this inflammation; removing the causes is more effective overall.

Consuming excess glucose and fructose continuously in food, increasing fructose production from the Polyol Pathway, and increasing body fat all lead to oxidative stress. Mitochondrial inflexibility results from the continuous use of either sugar or fat for energy production, yielding low energy output, which decreases energy flux.

Reducing or eliminating the causes of chronic stress will improve mitochondrial function and reduce oxidative stress. This approach is the best way to improve our horses’ health.

Final comment

The goal of feeding horses is to provide all the required ingredients to build, maintain, and power the horse. It is also to maintain efficient energy flux. Doing these will Help Horses Thrive In A Human World.™ 

1. Feed sufficient, high-quality protein first (all the essential amino acids), followed by a balance of carbohydrates (starch, free sugars) and fat (from cellulose) to maintain an appropriate body composition throughout the changing seasons. Maintain life-long, high-quality protein intake for healthy connective tissue, integument (hair, hooves), immune system, enzyme function, and neurotransmitters.
2. Feed horses as individuals, constantly adjusting the amounts of fat and carbohydrates to adapt to work, season, breed (genetics), and degree of chronic stress. However, always maintain the minimum amino acid needs.
3. Reduce environmental stress and allow quality rest to reset the hormetic set point.
4. Avoid grains and grain mixes with inflammatory ingredients and supplements until the basics are completed. Most of them do not work or are of suspicious quality. Few existed or were available ubiquitously 50 years ago, and the horses did well before we added them.