From Shana's Office Hours Episode 6, "Building an Equine Balanced Diet From the Ground Up."

Three flakes a day is not a measurement.

I say this in almost every Office Hours session, because it is the cleanest example of the gap between what a feeding program looks like and what it actually delivers. A flake from a 60-pound bale and a flake from a 110-pound bale are not the same flake. The horse eating "three flakes, twice a day" might be getting 12 pounds of forage. He might be getting 28. Without weighing, you do not know which.

This is the small version of a bigger problem. A balanced equine diet on paper and a balanced diet inside the horse are two different things. You can hit every nutrient target on a feed tag, write the math down, calculate the calcium-to-phosphorus ratio across the whole stack, and still end up with a horse that is not building topline, not holding weight, not recovering the way he should.

If that sounds familiar, you are in the right place. This article walks through the foundation of equine nutrition the way I teach it: what balanced actually means, the gaps most diets carry, how digestion changes what gets used, and the order of operations for building a program that works in the horse. Not just on paper.

Why the equine digestive system changes everything

Before we talk about what to feed, we have to talk about how the horse processes food. Because the anatomy sets the rules for the program.

Three things matter most.

First, horses are hindgut fermenters. Unlike cattle, they ferment fiber in the cecum and large colon, not a rumen. The microbial population in the hindgut does most of the actual nutrient extraction. When that microbial population shifts, the entire output of the digestive system shifts. This is why diet changes that happen faster than the microbes can adapt cause colic, loose manure, and off-feed weeks. The standard transition window is 10 to 14 days. That is not a recommendation. That is a biology constraint.

Second, the stomach is small. A horse's stomach holds only 2 to 4 gallons, and it is designed for continuous small meals. An empty stomach keeps producing acid, which is what causes ulcers. The horse is built to chew, not to gulp. Constant low-volume forage intake stimulates saliva production, and saliva is the body's own alkaline buffer against the acid the stomach is producing all day long. A horse with limited forage access is a horse with reduced buffering, regardless of what is in the bucket.

Third, the lining of the gut itself has to be functional for any of this to matter. Tight junctions in the intestinal wall regulate what crosses into the bloodstream. The villi, the finger-like projections that create absorptive surface area, are constantly being repaired and replaced. A horse under chronic stress has elevated cortisol, and cortisol drives faster villi turnover and shortening. Faster turnover and shorter villi mean less absorptive surface area available at any given moment, regardless of what is in the feed bucket.

That last point is the one I come back to most. A balanced diet only works if the horse can absorb it. The numbers on the hay analysis, the amino acid math, the vitamin E supplementation, all of it depends on a gut that can pull nutrients across the lining and into circulation. A compromised gut means the program runs on paper but not in the horse.

The six things a balanced diet has to deliver

A balanced diet for a horse has to deliver six categories in the right amounts and the right proportions.

That part is not controversial. Where most programs go sideways is in assuming that the presence of these inputs equals their function. It does not.

Energy comes from carbohydrates, fats, and protein, in that order of preference for most horses. Fiber is what the equine digestive tract was designed to process, and it should be the dominant calorie source. Fat is the cool-burning energy source, sitting at 2 to 4 percent of the diet for most horses and 6 to 10 percent added fat for athletes who need sustained slow-burning fuel. Protein quality, not just protein quantity, determines whether the body can build and repair tissue. Vitamins regulate the chemistry of every system. Minerals build structure and balance the electrolyte gradient that lets the muscles fire and the nerves transmit. Water is the one most people take for granted, and a 1,000-pound horse needs 5 to 12 gallons a day at rest, more in work.

There is one more layer to this. These six categories interact with each other. Calcium changes how phosphorus is used. Selenium changes how vitamin E performs. Zinc and copper compete with iron. Lysine sets the ceiling for how much of the protein the horse can actually build with. A diet that looks complete in six columns of a spreadsheet can still be unbalanced once you read across the rows.

That is what balanced has to mean. Not present. Proportioned, and absorbable.

Forage is the foundation, not the backdrop

If you do nothing else after reading this, get the forage right. Everything else is downstream.

Forage should make up the majority of every horse's diet. 1.5 to 2.5 percent of body weight daily. For a 1,000-pound horse, that is 16 to 25 pounds of forage every day. Never less than 1 percent of body weight, even on a calorie deficit. Drop below that and you are setting up ulcers, colic, behavioral changes, and deficiencies that no supplement can outrun.

Forage never drops below 50 percent of the diet, even for a horse in heavy work. If a horse needs more calories, you add forage first, then concentrate. If a horse needs to lose weight, you pull concentrate first, then forage. High-quality forage can provide 75 to 100 percent of the daily nutrients for most horses at maintenance. The pounds matter. The quality matters more.

A horse eating volume can still be deficient. If the hay is poor quality, the pounds do not matter. The only way to know what is actually in your forage is a hay analysis.

The targets to read against, for a maintenance horse: crude protein 10 to 12 percent dry matter, digestible energy 1.8 to 2.2 MCal/kg, ADF 30 to 45 percent (lower means more digestible), NDF 40 to 65 percent (lower means more palatable), NSC under 10 percent for metabolic horses, calcium-to-phosphorus 1.5 to 2 parts calcium to 1 part phosphorus. Never inverted.

A core sample sent to a forage lab costs about 30 dollars. Interpreting the analysis and turning it into a feeding plan that actually works for your horse, priceless. The information shapes every decision that follows. And while you are at it, weigh your flakes.

Matching energy to workload

Forage is the foundation. Concentrate is added only when forage and a ration balancer cannot meet the horse's protein and fat needs.

A maintenance horse can run on close to 100 percent forage if the forage is good. A horse in light to moderate work can usually hold weight and condition on forage plus a ration balancer. Heavy work and very heavy work are where concentrate earns its place, and even then, forage stays at 50 percent or higher.

Fat and fiber give slow-burning energy, what I sometimes call cool fuels. They are stable, they support sustained work, and they do not spike behavior. Starch is hot fuel, and it has a place for elite athletes with sustained high-intensity demand. For everyone else, hot fuel creates more problems than it solves: gastric ulcers, behavioral reactivity, hindgut acidosis when too much starch reaches the cecum.

The rule is simple. Add forage first. Then a balancer. Then fat. Then, only if you genuinely need it, concentrate with starch.

Protein is about amino acids, not percentages

The number on the feed tag is crude protein. The number that determines whether the horse can build and repair tissue is the amino acid profile.

Lysine is the first limiting amino acid. If lysine is low, total protein intake stops mattering. Protein synthesis is capped at the level the first limiting amino acid allows. Threonine is second, methionine is third. These three set the ceiling on what the protein in the diet can actually do for the horse.

Legumes, alfalfa, and flax are the strongest practical sources. A maintenance horse needs 8 to 10 percent crude protein. Light to moderate work pushes that to 10 to 12. Heavy work, 11 to 16. Growing horses, 14 to 16. Lactating mares, 12 to 14. But the percentage is the floor of the conversation, not the ceiling. If the amino acid profile is wrong, more crude protein is more nitrogen in the manure, not more muscle on the horse.

The micronutrient gaps where diets usually fall short

Most feeding programs that look good on paper have the same handful of holes underneath. None of them are exotic. All of them are correctable.

Vitamin E drops the moment hay is cut, and keeps dropping in storage. Any horse off fresh pasture, in most parts of the country for most of the year, is sitting on a deficiency. It may not show up immediately on a clinical exam, but it will show up on blood work, and it shows up clinically over time in muscle integrity, neurologic function, and oxidative stress recovery. Stalled horses without pasture access typically need 1,000 to 2,000 IU per day.

Selenium varies dramatically by region. Soil-deficient areas produce hay that cannot supply what the horse needs, and the only way to know what your soil is doing is to test it. Selenium and vitamin E work as a pair, and the deficiency of one accelerates the impact of the other. Selenium also has a narrow safety margin. Test first.

The calcium-to-phosphorus ratio has to lead with calcium. The target is 1.5 to 2 parts calcium to 1 part phosphorus. Inverted ratios pull calcium out of bone. A stacked supplement program where individual products each look reasonable can compound to push that ratio somewhere it should not go.

Magnesium supports nerve and muscle function. Sodium and chloride drive the electrolyte gradient. Copper and zinc support hoof quality, immune function, and coat. Most grass hays are borderline on copper and zinc, and a 4:1 zinc-to-copper ratio is the supplementation target.

This is where a ration balancer or a targeted mineral supplement does its real work, filling the gaps the forage cannot cover.

Why diets fail in the real world: bioavailability and absorption

Here is where the conversation gets practical. Bioavailability is the word for the gap between what is in the feed and what the horse actually uses. A balanced diet on a spreadsheet assumes 100 percent bioavailability. Real horses do not operate at 100 percent.

A few of the most common drivers:

Age and digestive health change absorption efficiency. A 22-year-old horse with reduced gut motility and partial dental compromise is not absorbing the same percentage of his feed that a six-year-old in steady work is. The same diet produces different outcomes in different horses.

Imbalance between nutrients reduces absorption of both. Excessive phosphorus blocks calcium uptake. High iron interferes with copper and zinc. Two quality products can each be doing their job and still create an interaction that reduces the effectiveness of both. A supplement stack (every supplement, balancer, and concentrate the horse is getting, looked at together rather than one product at a time) that has not been reviewed as a whole is operating on the assumption that nothing is competing, and that assumption is usually wrong.

Soil depletion shapes what is actually in the hay. Hay grown on depleted soil cannot supply minerals that are not in the ground to begin with. This is regional and seasonal. The same field can produce very different hay across cuts, weather years, and management practices. Your last hay analysis is not a permanent description of your hay.

Storage degrades nutrient content. Vitamins A and E oxidize on exposure to air and light. Moisture promotes mold growth. Hay stored badly for six months is not the same hay you put up. Feed that has been opened and partially used for weeks is not the same feed you bought. Sealed containers, cool temperatures, and minimal light exposure preserve what is actually in the bag.

And the largest driver: stress, digestion, and absorption. Stress raises stomach acid levels, and elevated acid decreases both digestion and absorption. A compromised lining means nutrients pass through without reaching the muscle, the hoof, the immune system, wherever they are needed. The horse eats. The food moves through. The nutrients do not arrive.

These are not failures of effort. They are failures of the assumption that "balanced on paper" means "balanced in the horse."

When supplements help, and when they do not

Supplements help when they fill a documented gap. They do not help when they are added to a diet that has not been measured, or when they layer onto a gut that is not absorbing what is already there.

The honest answer for most horses is that a forage analysis plus a ration balancer or a feed concentrate based on what the analysis shows will close most of the common gaps. Beyond that, specific supports earn their place when there is a genuine need.

Often needed: vitamin E for any horse off fresh pasture, selenium in deficient regions, salt for any horse in work, copper and zinc for hays that are typically low. Rarely needed: iron (almost never deficient, and excess interferes with copper and zinc absorption), vitamin A (abundant in good hay, and fat-soluble, so excess accumulates and causes toxicity), B vitamins (synthesized by hindgut bacteria, only needed if the gut is compromised), vitamin C (horses make their own).

The temptation in the supplement industry is to add. The discipline of building a balanced equine diet is to measure first, fill the actual gap, and reassess.

Before you add any supplement, ask the six questions on this checklist.

If you cannot answer yes to all six, the supplement is not earning its place in the program yet.

Building a balanced equine diet from the ground up

If you want a build order to follow, this is the one I walk through with owners.

1. Weigh the horse. A weight tape will get you close enough to start. Body condition score gives you a second data point.
2. Test the hay. Send a core sample to a forage lab. The cost is minimal. The information shapes every decision that follows.
3. Set forage intake at 1.5 to 2.5 percent of body weight. For a 1,000-pound horse, that is 16 to 25 pounds of forage per day. Never below 1 percent. Forage never drops below 50 percent of the total diet, even for a horse in heavy work. Weigh the flakes.
4. Fill the documented nutrient gaps. A ration balancer or a targeted mineral supplement, based on what the hay analysis showed. Not what the marketing said. What the lab showed.
5. Add concentrate only if forage plus balancer cannot meet the horse's protein and fat needs. Hard keepers, heavy work, and seniors are the usual candidates. Fat and fiber give slow-burning energy. Starch is the option of last resort.
6. Monitor and adjust. Body condition, season, workload, illness, age, all of it shifts the equation. The program is a moving target.

And one more thing. Change the diet slowly. Any change takes 10 to 14 days. The hindgut microbes need that long to adapt. Rushing the transition is what causes the colic, the loose manure, and the off-feed week you did not plan for.

Frequently asked questions

What to take from all of this

Most feeding programs that are not working are not failing for the reasons the owner suspects. The horse is rarely missing some exotic input. He is usually missing the foundation. Forage measured, gaps identified, transitions paced, gut functional enough to absorb what is in the bucket.

If you do nothing else after reading this, weigh your hay this week. Send a sample to a forage lab. Pull the labels of every supplement your horse is on and look at the calcium, the phosphorus, the iron, and the lysine across the whole stack. You will find one of two things. Either the program is sound and you can stop questioning it, or you will find the gap that has been quietly holding the horse back.

If you find the gap and want help turning it into a plan, that is exactly what my one-on-one consultation is for. 60 minutes together, a full review of your horse's program, and a written plan you can act on. The link is consult.scooprx.com.

Fine is not the goal. Capacity is.

Author: Shana Winkel, PhD, Equine Nutritionist