Feeding Your Horse (Part 3) - Nutrients

what nutrients does your horse need?

So far, we have run over calculating your horse’s energy requirements, and how to feed your horse. Today we will examine the actual benefit and use of their nutrients.

This guide will be exceptionally useful if you find your horse experiences regular issues such as laminitis, dry skin or low immunity.

Macronutrients (Carbohydrates, Fats, Protein)

Macronutrients provide the bulk of our horse’s energy or calorie intake. They also serve an important function in the overall way their bodies work.

Carbohydrates (sugar, starch and dietary fibre)

Carbohydrates form the bulk of feed for horses and comprise of 2 main categories – simple carbohydrates and complex carbohydrates. Sugars and simple carbohydrates and starch and dietary fibre fall under the category of complex carbs.

Starches and simple sugars are found most commonly in grains and concentrated feed. Excessive levels of these can contribute to blood sugar fluctuations and potentially contribute to conditions such as laminitis, cushings disease and tying up. Starches and simple sugars are easily digested absorbed by the small intestine. Starches require a particular enzyme to be broken down into simple sugars before they can be absorbed, and thus can become overloaded when a large quantity of concentrated feed is eaten, making it important to provide these in a limited quantity per feeding (see Part 2 for more information)

Dietary fibre or ‘roughage’ is exceptionally important for horses. Their gastro-intestinal tract, which actually is similar to humans in make-up, has evolved over several millennia to be able to ferment and digest the maximum quantity of nutrition out of dietary fibre. The ceacum(the equivalent to the now redundant human appendix) is responsible for housing the bacteria and protozoa that helps ferment and break down fibre for use within the body. The intestinal tract of the horse is also quite long, allowing a slower transit of food for maximum nutrient absorption.

The Glycemic Index (GI) is a description of how much a feed increases blood glucose level. Foods with a high GI increase blood sugar quickly. Foods with a low GI still affect blood sugar levels, but not as much or as fast.

Physical effects of high GI feeds

High GI feeds can generally be eaten faster. Less chewing produces less saliva. Saliva provides a buffer in the stomach to neutralize the acid, so less saliva can lead to more acid in stomach and result in stomach ulcers

High GI foods tend to move faster through the gut, which can create colic.

The speed and high sugar may create abnormal or unhealthy bacterial growth in the ceacum, which influences the development of inflammation, toxin release, colic and laminits.

Sugar and starch is absorbed quickly resulting in fluctuations of blood glucose level and insulin release. This increases the risk of cushings, laminitis, colic, tying up and equine metabolic syndrome

Foods with a high GI

Foods with a high Glycemic Index are high in sugar and often low in protein and fat. Most commonly are seeds and grains, as they contain all the sugar a seed requires to sprout. Sprouted seeds contain less sugar and therefore are a lower GI. Examples of high GI foods include:

  • Sweet feed
  • Corn
  • Oats
  • Barley

Foods with a low GI

Foods that are low GI are generally high in fat or protein AND dietary fibre. Most commonly examples are the hulls of the seed and also:

  • Wheat bran
  • Speedi‐beet
  • Alfalfa
  • Rice bran
  • Soy bean hulls
Energy and Protein in horse feeds



Despite being herbivores, horses still need protein. This doesn’t mean you need to run out a cook up a steak or two (would you eat your former neighbor anyway?) as horses can receive and digest amino acids, the building blocks of proteins, from plants.

Protein is an important part of growth and is require as building blocks for muscle and other body tissues. It is also essential for healing and repair as well as general function, including the production of enzymes and hormones. Thus protein is an important component of the diet, even though it is only required in smaller amounts.

Mature adult horses require 8-10% of the total feed to consist of protein. Working doesn’t significantly impact this though we tend to feed at the higher end of the ratio to help recovery (bearing in mind that a horse in work has a higher energy requirement, so the same size horse in work will receive more grams of protein, but could still be fend the same percentage of protein in feed as a non-working horse). A young horse in growth stage requires significantly higher percentage of protein in their feed, being between 14-16%, to help with the growth phase. Geriatric horses also may need a similar protein percentage to growing horses (as their ability to effectively use protein decreases, their oral intake may need to increase), but their liver and kidney functions should be examined prior to increasing the feed as higher protein diets make these organs work harder and may exacerbate deterioration.  Pregnancy and lactation also need higher protein than a mature adult horse.

Below are some protein averages in common feeds, and you can see more specific protein requirements in the earlier chart.


nutrient requirements msd mercks vet manual.png


Fat has a bad reputation, but is critical for our overall function. Omega 3, 6 and 9 play important parts in our inflammatory processes, vitamin absorption, and offer twice the energy to protein or carbohydrates on a per gram basis. The benefits of a high fat diet is generally that you can feed smaller quantities and provide more energy, but using the correct ratio of omega 3/6/9 can have significant benefits on overall health, and particularly for skin and coat issues.

Feeds that are high in fat include mill run, rice bran and wheat bran.

However, overfeeding high fat feeds can result in the deposit of fat around the liver and heart which is not beneficial to the horses overall health.



Micronutrients are nutrients that don’t provide energy but are essential for the body to function accurately. These are our vitamins and minerals, and also include some substrates that act in vitamin-like ways.

The list of micronutrients is extensive, so we will focus on a key few. If you are keen to know more, you can read them here in the MSD Mercks Veterinary Manual.

Calcium & Phosphorous

Because of the way our horses are built and work, the skeletal frame is exceptionally important and therefore calcium and phosphorous should be given some important considerations.

Nutritional Excess and Deficiencies in Horses

"Excessive intakes of certain minerals may be as harmful as deficiencies; therefore, mineral supplements should complement the composition of the basic ration. For example, if the horse is consuming mostly roughage with little or no grain, phosphorus is more likely to be in short supply, especially for growth, than calcium. However, if more grain than roughage is being fed, a deficit of calcium is much more common. The total mineral contribution and availability from all parts of the ration (forages and roughages, concentrates, and all supplements) should be considered when evaluating the mineral intake." Merck Vet Manual

Calcium and phosphorous are required in greater quantities during growth, pregnancy and lactation than for a mature horse. Geriatric horses may require higher phosphorous than mature horses but calcium should be monitored and reduced, especially if renal function is compromised.

Both calcium and phosphorous play an important part in the development of bone, but also in areas such as cell membrane protection and neural function. The calcium:phosphorous ratio should be in balance of ideally 1.5 calcium to 1 phosphorous.


Salt (sodium chloride) requirements are largely influenced by the work, or more accurately, sweat production. Horses will generally self regulate salt intake and as such should have free access to salt blocks or licks.

A Note about Supplements and Additives

  • Multi vitamin – find a well reputed source to ensure the horse gets its dietary vitamins and minerals
  • Oil – calorie dense option to increase weight. Feed no more than 500mL. 250mL of oil has roughly the same calorie content of 2.5kg of oats. Balance of omega 3, 6 and 9 is important in feeding oil. Try to avoid over feeding omega 6. Ensure that you use cold pressed oil and store in a cool environment out of direct sunlight.
  • Soybean meal ‐ contains the full spectrum of essential amino acids. Great sources of protein for muscle mass and over health
  • Psyllium husks – 1 cup a week can help maintain motility of bowels and may reduce incidence of colic

There are plenty of other supplements and additives each with their own merits. Horse feed is an art not a science, if you find something that works for your horse use it, if you are using something that doesn’t seem to be working, don’t use it. Feeding horses is expensive enough without feeding additives that aren’t doing anything!

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