Corn is an economical energy source found in many complete feeds for horses. Corn is also sometimes fed as a standalone concentrate for horses that need additional calories in their diet, such as exercising horses, growing horses, or mares in the late stages of pregnancy or early lactation.

Corn products come in many forms, including whole, cracked, meals, oils, silages, and syrups. Different forms of corn provide differing nutrient compositions, making it a versatile feed ingredient for livestock.

However, due to the high starch content of corn grain products, they should be incorporated into the diet cautiously and avoided when high starch or energy intake is unnecessary. Feeding too much corn poses a risk of digestive and metabolic issues.

Grain-based feeds like corn should always complement your horse’s forage, not replace it. Horses should ideally be fed a balanced, forage-based diet with concentrates added only as needed to meet their specific nutritional requirements.

Corn for Horses

Corn (Zea mays L.) is a common agriculture crop that belongs to the grass family. While corn originated in the tropics, it can be grown in a wide range of climates.

The United States boasts the highest production of corn in the world, with 38% of global production occurring in the country. [1]

Corn is cultivated for a wide variety of purposes, such as human and animal foods, as well as biofuel production and more. While it can be used for many purposes, corn is one of the most productive food-producing plants, making it an important food source for humans and livestock animals alike. [1]

Many types of corn products are fed to horses, including:

  • Whole corn
  • Cracked corn
  • Corn meal
  • Steamed corn
  • Steam-flaked corn
  • Micronized corn
  • Popped corn
  • Corn oil
  • Corn silage
  • Corn distiller’s grain
  • Corn cobs
  • Raw corn
  • Corn syrup

The nutrient profile of corn depends on its processing method. Products like cracked and steam-flaked corn have nutrient profiles similar to whole corn, though their digestibility may be altered. Conversely, corn products like corn oil and corn syrup have a significantly different nutrient profile.

Table 1. Nutritional composition of select corn products compared to oats and barley. [2][3][4]

Feed Energy (Mcal/kg) Protein (%) Starch (%) Sugar (%) Neutral Detergent Fiber (%) Fat (%) Calcium (%) Phosphorus (%)
Shelled Corn 3.85 8.8 70 2.7 9.9 4.2 0.04 0.3
Steam Flaked Corn 3.88 8.2 72 2.4 9 3.4 0.03 0.2
Ear Corn 3.63 8.5 60 3.8 19 3.7 0.06 0.3
Corn Silage 2.60 8.3 33 2.0 43 3.3 0.23 0.24
Corn Oil 9.00 0 0 0 0 100 0 0
Corn Syrup 2.86 0 0 77.6 0 0 0.02 0.01
Oats 3.35 12.5 43 2.2 27 6.1 0.11 0.4
Barley 3.66 11.9 54 3.4 19 2.4 0.10 0.4

Forms of Corn for Horses

The wide variety of corn products on the market and their differing nutrient profiles can make it difficult to determine whether and which type should be included in your horse’s diet.

Usually, horse owners add corn products to equine diets to increase calorie intake. Determining the best source of calories for your horse can help make the choice simpler.

Adding Starch with Corn Grain

Products such as shelled (whole) corn, processed corn grain, and ear corn (corn on the cob) provide energy mainly in the form of starch. This is similar to other grains such as oats and barley.

Although corn tends to have a higher energy and starch content compared to oats and barley, feeding corn results in a similar glucose and insulin response to other grains. [5]

Corn Processing

A corn kernel consists of a starch-rich endosperm surrounded by a fibrous hull. The fibrous outer layer of corn has lower digestibility compared to the starch in the endosperm.

This means that the energy from the starch is more readily available to the horse, while the fibrous hull provides less nutritional value and is harder for the horse to break down. For this reason, processing corn to disrupt the hull can make the starch inside more available for digestion. [6]

Starch can be digested in both the foregut and the hindgut of horses. Digestion of starch in the small intestine results in absorption of glucose, a potent energy source.

Starch that is not digested by enzymes in the small intestine travels to the hindgut, where starch-fermenting microbes consume it to produce volatile fatty acids and lactic acid. Although volatile fatty acids do serve as an energy source for horses, the lactate produced alongside starch fermentation can disrupt the hindgut microbiome and even lead to hindgut acidosis.

Improving the foregut starch digestibility of grain allows the horse to extract more energy in the form of glucose, potentially reducing the risk of excess starch reaching the hindgut, where it could cause digestive problems.

Common processing methods for grains in horse feeds include mechanical, thermal, and thermo-mechanical treatments. [6]

  • Mechanical processing: Rolling, crushing, or grinding grains can break their fibrous shells, making starch more available for digestion.
  • Thermal processing: Roasting or micronizing grains exposes them to high temperatures and pressures, which expands the grain and gelatinizes starch to improve its availability.
  • Thermo-mechanical processing: Flaking, popping, and extruding combine mechanical and thermal processes to both break the outer shell of grain kernels and gelatinize the starch to improve its availability.

When comparing processing methods like cracking, grinding, and steam processing of corn, steam-flaking often results in a greater glucose response, indicating improved starch digestibility. [7][8] However, other research examining the effect of finely grinding, steaming, micronizing, steam-flaking, and popping corn showed no difference in glucose and insulin response. [9]

It’s worth noting that in some cases, the digestibility of starch in corn is improved with processes like micronizing, but there is no difference in glucose and insulin response. [10]

Adding Fat with Corn Oil

Similar to other oils such as soybean, canola, and flax oil, corn oil is a rich source of calories from fat.

Oils are composed of nearly 100% fat. Corn oil is primarily composed of polyunsaturated fatty acids (59%), but also contains monounsaturated fatty acids (24%) and saturated fatty acids (13%). [11]

Closer examination of the polyunsaturated fatty acid profile of corn oil reveals that it predominantly comprises the omega-6 fatty acid linoleic acid, with only a small amount of the omega-3 fatty acid linolenic acid. This gives corn oil a very high ratio of omega-6 to omega-3 fatty acids, at 83:1. [11]

This omega-6 to omega-3 ratio is considerably higher than other common oils used for horses such as soybean oil (4:1), canola oil (2:1), and flax oil (0.3:1). [12][13][14]

Adding Sugar with Corn Syrup

Corn syrup is created by breaking down the starch from corn to its constituent glucose molecules. This produces a sugary syrup mix of glucose from corn.

Corn syrup can be used to sweeten commercial feeds to improve their palatability. It can also be used as a top-dressing for unsweetened feeds to encourage consumption.

Due to its very high sugar content, corn syrup should be used sparingly to avoid glucose overload. It should also be avoided in horses that are sensitive to sugars or excess calorie intake, such as horses with metabolic problems or easy keepers.

Adding Fiber with Corn Silage

Corn silage is made by cutting corn plants (stalk, leaves, grain, and cob) and fermenting them. This produces an energy-dense forage c