By Brian Eitelman, DVM, CJF

Horses eat hay - it’s simple and it’s the truth.  They evolved over millions of years grazing on grasses all day.  Hay, above all else, should be the overwhelmingly main ingredient in their diet.  Before you invest time and money in supplements, invest in your horse’s hay.  It is a far better allocation of limited resources for you and far better nutritional outcome for your horse.

Here’s a simple breakdown of dietary basics for horses:

The average horse needs to eat 1% of its body weight per day in good quality hay.  For example, the average horse weighs around 1000 lbs.  A 16 to 17 hand warmblood may come closer to 1300 lbs.  Unless you have a large warmblood, assume your horse is average.  So, 1% of body weight for an average horse is 10 lbs, while 1% of body weight for larger horse is 13 lbs.  Therefore, the food intake for an average horse should be around 10 pounds per day.  The upper limit for the amount of hay that a horse can physically eat in a day is only 2-3% of their body weight.  Thus, the most a horse can physically eat in one day would be 20-30 lbs for a smaller horse and 26-39 lbs for a larger horse. 

So, how do you figure out the weight of the hay you are feeding? 

The weight of a bale of hay can vary greatly depending on the type of hay (grass or alfalfa), the setting of the baler, and the size of the bale.  Light bales can weigh as little as 40-50 lbs and heavy bales can be 80-90 lbs.  Don’t have a scale handy?  If you pick up a bale and think “I could throw this on to the top of the stack or across the yard,” you probably have one closer to 50 lbs.  On the other hand, if you think “I need to put this bale at the bottom of the stack or just go ahead and cut the strings right here,” you’re probably in the 80-90 lb range.  Therefore, an average horse should only need to eat 1/4 of a small bale, 1/5-1/6 of a normal bale, or 1/7-1/8 of a larger bale per day.  This should meet the nutritional needs of your horse for the normal day-to-day requirements (including low levels of exercise, standing around, walking, playing, etc). 

This rule generally applies for good quality hay (that is less than about a year old).  Now we’ll look at the exceptions to these rules:

• The first exception involves heavy levels of exercise and activity. “Heavy exercise” is greater than 30 minutes of prolonged vigorous activity (long trotting, extended trail rides, roping 15+ head), after which your horse is huffing and puffing and sweating. Walking in circles, stopping to post on Instagram, lunging for 5 minutes to “get the hump out,” and then doing 10 minutes of jumps or spins doesn’t take that much of a toll on your horse. They are built for endurance and efficiency.

• Use some common sense with this. First, make sure your horse is in appropriate physical condition to perform to that activity level. Second, if your horse is only exercising once a week, you haven’t changed the nutritional requirements of him/her that much. When your horse is involved in heavy exercise several times a week, then it’s time to start looking at what the extra demands on its body are.

• The second exception is for young growing horses, broodmares, and underweight horses. The simple principle is that you are not just trying to meet current nutritional demands but provide additional support for future energy needs. Think short term steps with this. Feed the four-month-old for the requirements they’ll have as a five or six-month old, not as a two year old. Increase the broodmare's feed as the demands of pregnancy and lactation dictate. Feeding a mare who’s 60 days along as if she’s at 300 days will only cause her to be overweight and more likely to have problems at time of delivery. A rescued horse that weighs 800 lbs (but should be at 1100 lbs) can only put on weight so fast. A feed plan more equivalent to a 900- or 1000-pound horse will result in less wasted feed and a healthier, steadier recovery to appropriate body condition.

• The third exception is a broader category of malabsorption/maldigestion. There is almost always an underlying medical cause for these issues. Some of which are correctable; some are not. Basically, the horse is getting an appropriate amount of good quality hay for its age and activity level, but he/she is either losing weight or unable to gain weight. Poor dental condition and parasites commonly contribute to this problem and are often easily corrected. More difficult conditions to help include changes in the gastrointestinal tract that result in a decreased ability to either break down the nutrients or properly absorb them (think horses with chronic diarrhea).

Investing in quality dental care will likely go farther than you think for improving digestion and feed efficiency.  Additionally, intelligent and targeted deworming (not overuse of dewormers by following the feed stores recommended “every-8-week deworming”) will not only improve nutritional status, but also overall health status, of your horse.  Not sure how often to deworm and what to use? ASK YOUR LOCAL VET and WATCH the "Ask a Farrinarian" blog on "Parasite Management and Deworming Strategies."

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We have now come to the crux of the matter - should you supplement your horse's feed???

The first question to ask is - Is my horse getting the proper amount (weight) of hay?  

Most horses are.  For most horses, the maximum daily intake is not a concern.  Most horses have a sufficient amount of feed in front of them for a sufficient time to meet their needs.  A problem arises when either:

1) Even with unlimited good quality hay, the horse isn’t able to eat and digest enough nutrients to maintain and repair its body.  Example: The geriatric horse with poor teeth and/or underlying disease process that prevents proper digestion/absorption.

2) The horse is routinely at a level of exercise that puts greater demand on its body than it can replenish with the maximum amount of hay it can eat.  Example: A school horse or polo horse that has strenuous activity 3-5 hours daily, multiple times per week.

 In the above circumstances, supplementing with a name brand senior feed is a great place to start.

** As a side note, I commonly see a problem in herd settings. Often, a sufficient amount of hay is fed, but it isn’t spread out enough, which allows the dominant horses to keep the others from eating.  If you’re unsure, just take half a day and watch.  Is everyone eating when they want?  If a horse is pushed away from the hay, can it go find another pile?  If not, consider rearranging the feeders or simply spreading out the hay more. **

The second question is - what is the nutritional content of the hay I am feeding?  There are some simple rules of thumb to follow:

• All things being equal, alfalfa typically has higher protein content than grass.

• Higher altitude hay typically has higher sugar (carbohydrate) content than the same species grown at lower altitude.

• Newer hay has more nutritional content than older hay.

• Cuttings: 1st cutting will have more bulk/pounds of feed per bale. Because the first cutting will include everything that grew in the pasture since the final cutting last summer, the nutritional content will be more inconsistent. Each successive cutting will have less bulk/pounds of feed per bale than the previous but will be more energy-dense and have more consistent nutritional content. 2nd cutting will be richer than the 1st. 3rd cutting will be richer than the 2nd. In most conditions, 4th cuttings and beyond are just too energy rich for horses to tolerate well.

The best way to get a numerical answer and start the process of diet supplementation: HAY ANALYSIS!!!!  This simply involves collecting some samples (from multiple bales or areas of the pasture) and sending them to any feed analysis center - this is usually a county extension agent, but just google it for the nearest location.  This analysis usually costs around $20-30 and is one of the best investments you can make.  Simply put, it takes a lot of the guess work out and you have a much better idea of what you’re actually feeding. 

The next step, now that you know what is in your horse’s hay and how much it is eating, where are the holes?  What does he/she still need?  You can then precisely and economically select the right supplement for your horse and feed it in the appropriate amount. 

** IMPORTANT - Beet pulp - This is one of the most common supplements fed to horses and one of the most misunderstood.  In truth, beet pulp is empty fiber.  It has almost no nutritional value.  DO NOT feed this expecting your horse to gain weight with it.  The only role of beet pulp is as a bulking agent in a diet that consists of mostly grains/supplements and very little hay.  For example, it can be given to a geriatric horse with no teeth that is unable to eat hay.  In this case, you can effectively use beet pulp to replace the fiber role of the hay.  ** Warning: Beet pulp will absorb large amounts of water and needs to be properly soaked for hours before feeding to minimize choking hazard!!! **

I want to take a moment and re-emphasize the importance of feeding quality hay.  It’s also better to feed your horse more times per day, in smaller amounts with each feeding.  However, reality dictates that sometimes we have to be honest and say that we aren’t able to follow “best practices.”  It’s ok, I get it.  Just do the best you can.

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DISCLAIMER:  The next section is full of somewhat dry, detailed information about nutrition.  If you are really interested in getting into the nitty gritty of feed analysis, please READ ON :).  If not, skip to the bottom of the page for the summary.

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So, let’s break down a feed analysis and the categories of NUTRIENTS that we’re worried about. 

There are three categories for measuring energy in a feed ration:

• Gross energy (amount of potential calories/energy)

• Digestible energy (amount of energy actually digested and utilized by body)

• Undigestible energy (the stuff that ends up back in the stall or pasture)

** Most hay/forage analysis will contain estimates for digestible energy, but these are just estimates.** 

The elements of feed that contain energy are 1) carbohydrates, 2) proteins, and 3) fats.  The final component of feed is 4) vitamins and minerals.

1. Carbohydrates are the main source of energy and also play a key role in utilization of the other energy sources.  They can be broken down into fibrous and non-fibrous.  More fiber (stems/stalks/shells/husks) means less digestibility.  However, nondigestible fiber is important in nutritional health as a bulking agent.  Grasses and plants have more fiber per pound than grains, whereas grains are higher in digestible carbohydrates.  Likewise, lush, green pastures have more digestible energy than that same pasture in fall/winter when the fiber content of the grasses has increased. 

 2. Protein: Horses utilize protein for multiple important body processes as well as for development and repair of muscle tissue.  Protein is also one of the most important nutrients from promoting hoof growth.  Excess protein needs can usually be met by simply feeding a larger amount of quality hay.  Protein needs are usually met when the overall increased energy needs of the horse are met.

3. Fat is an extremely good source of energy.  In general, utilized fat produces twice as much energy as carbohydrates.  However, in order to properly utilize fat, the body needs sufficient carbohydrates.  Without carbohydrates, mobilized fat produces little energy and potentially toxic compounds, and what is left just reverts back to fat.  Grains and other supplements typically have a higher fat content than hay. 

4. Vitamins/Minerals: Minerals are needed as components of body tissue for various processes.  The main minerals needed are calcium and phosphorus.  Ideally, diets have a calcium/phosphorus ratio of 1 - 2 times as much calcium as phosphorus.  Copper and zinc are needed in much smaller amounts.  The mineral needs can typically be met with a trace mineral block. 

Minerals have a long lifespan and will be there in reliable numbers for the reasonable life of your feed.  Vitamins, however, tend to be far less stable.  Therefore, as your feed ages, you’ll be more likely to need to supplement them.  In general, the need for vitamin A is greater than the need for vitamins D and E.  Horses typically do a sufficient job of producing vitamin B.  Over-supplementing vitamins and minerals is one of the most common management errors.  More is absolutely not better, and these need to be supplemented in precise amounts!!

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In conclusion, here are some KEY take-away points:

1) Investing in good quality hay pays for itself in supplement savings AND overall digestive and nutritional health of your horse.

2) Knowing how and when to supplement your horse, rather than just feeding what everyone else does, is critical to getting the most out of your athlete.  This ensures putting the appropriate resources (time and money) into the best places and getting the most bang for your buck.

3) The best supplement you can provide is additional hay and more time to eat it.

4) The second best supplement you can provide is a name brand “senior feed.”  Senior feeds are intended to be a complete ration for older horses that are unable to eat sufficient amounts of hay.  These feeds will likely have appropriate levels of all the needed nutrients in a very concentrated form.  Feeding a good senior feed is a great and safe way to start down the supplement road with minimal risks.

5) Management/husbandry is an understated and absolutely critical element of care for your horse.  Spend the time to make sure their feed is given in an efficient manner.  Give them as much room as possible - don’t make them choose between starving and getting pinned in a corner and kicked.  Separate the feedings into as many times daily as possible.  The body can only digest, utilize, and store a certain amount of each nutrient at any one time.  Fewer feedings in larger amounts mean less utilization and more waste than more feedings in smaller amounts.

Thanks for reading!

Brian