Equine Winter Nutrition

Come the days of long shadows, when the sun lies low in the sky, jeweled leaves crumble and fade away, and the wind's crispness hints of the cold, gray days on the way. The pasture dies down. It's time to start getting extra fuel into your horses. Unless you live where temperatures are warm year-round, they need extra energy to stay warm through the winter. This is due to increased energy demands of cold weather and reduced nutrition in pasture.

Adjusting the Thermostat

Explains Karen E. Davison, PhD (equine nutrition), manager of equine technical service at Land O'Lakes Purina Feed, "All warm-blooded animals, including horses, have a critical temperature. This is the outside temperature below which a horse must produce extra heat to maintain its body temperature." That temperature varies, depending upon the horse's condition.

Davison says a mature horse in good flesh, where ribs cannot be seen, has a critical temperature around 30ºF during early winter. "After developing a winter coat and gaining 100 pounds, the critical temperature may be reduced to around 15ºF. It's estimated that young horses, horses in thinner condition, and those that have been stabled and not developed a winter coat might have a critical temperature around 40°F. When wind or wet conditions are present, the critical temperatures will be higher, as well."

A horse's critical temperature also depends on cold extremes. Says Carey A. Williams, PhD (equine nutrition), the equine extension specialist at Rutgers University Equine Science Center, "It's going to be different in northern Wisconsin as compared to Georgia in the winter months. As horses grow a winter coat, they are allowing their critical temperature to decrease, making them more comfortable at lower temperatures. So, zero degrees to a horse in Wisconsin will be the same as about 30 or 40 degrees to a horse in Georgia."

Reduced quality in forage (i.e., poor winter pasture) also results in less feed energy that can be used to generate heat. And Williams reminds that poor-quality hay has even further reduced vitamin and mineral content. "In terms of nutrient levels in forage from highest to lowest, it's generally green pasture, winter pasture, good-quality grass hay, and poor-quality grass hay."

Horses eating from a bale of hay don't receive the same nutrition as when they were grazing on the pasture from which that bale was harvested. "Horses select younger, more immature forages when they graze and have the option, but when pasture is allowed to mature enough to cut hay from, it is of lesser nutritional value than the younger forage," says Davison. (Not to mention the drying process from the sun denatures [destroys] a lot of the vitamins that were once present went the hay was green pasture.)

Turning Up the Heat

Horses require about 15-20% more feed for each 10°F the ambient temperature falls below critical temperature in order to produce extra heat, says Davison. "However, thin horses or horses with short hair may need even greater increases in dietary intake to maintain normal body temperature," she adds.

Extra hay is the best source for gaining extra winter energy. "Hay helps keep them warm through the heat of fermentation produced in the hindgut when digesting/ fermenting forage," reports Williams.

Easy keepers can do fine on free-choice grass hay, says Williams. Hard keepers need free-choice, good-quality grass hay or grass/legume mix plus a grain supplement. "Horses still in training during the winter should be fed similar to the hard keeper, plus added electrolytes on days when they're sweating because of their heavy hair coat," she says.

Extra protein isn't necessary for the average horse fed good-quality forage--easy keepers can maintain themselves on 10% protein in the total diet. However, additional protein can be beneficial for horses that are hard keepers, growing, or in training. Williams recommends an alfalfa/ grass hay mix for this group to increase the protein level of the diet. She notes that alfalfa does not cause a horse to become excitable, a common misconception of high-protein feedstuffs.

If your horse is getting poor-quality grass hay, which often contains only 6-8% protein, you should increase the protein level by adding alfalfa or soybean meal to the diet, Williams advises. If grain is part of your horse's daily feeding management, look for a grain that has about 14% protein to offset the potentially low protein in the hay. See "Analyzing Forages" at www.TheHorse.com/ViewArticle.aspx?ID=6172 for more information on evaluating protein content.


Consider adding a multi-vitamin/mineral supplement if you're feeding lower-quality forage. "Be careful when buying special 'winter supplements,' " Williams says. "Most of these are just multi-vitamin/mineral supplements, but cost more because they are called 'winter supplements.' Really, any multi-vitamin/mineral will do as long as it is formulated for horses. Some vitamin and mineral supplements are formulated based on the type of forage that is provided for the base of the diet (grass or legume hay, pasture, etc.). Make sure to read the label closely before purchasing and match it to the bulk of your horse's diet."

In other words, there aren't any specific nutrients you should supplement in cold weather vs. warm weather; supplementation is just based on the seasonal change in forage nutrient intake that occurs in horses on pasture (Just as long as the horse is normally on a balanced diet.)

When choosing a supplement, check the label and only buy something that tells you the actual ingredients, Williams urges. "For example, something that claims to have high levels of antioxidants, probiotics, vitamins, and minerals in a 'special formula' is a little fishy and would be best to steer away from," she says. "Stick with something that tells you specifically what vitamins and minerals are in the product and how much."

How quickly a supplement begins to produce an effect depends on the type of supplement. "If its base is water-soluble, then only a couple of days to a week is needed," says Williams. "If it is fat-soluble, it may take a couple of weeks to months."

Oats vs. Corn

In addition to increasing hay rations, some owners prefer switching from oats to corn or a sweet feed in the winter, Davison says. "The change from oats to corn or a sweet feed is based on the impression that corn or sweet feed is a 'hotter' feed than oats. This concept of oats being a summer feed and corn a winter ration has some merit, but also has some flaws."

Davison gives the nutritional comparison between the two rations:

"One pound of corn has more energy and is lower in protein and fiber than one pound of oats," she says. "But not only does corn have more energy per pound than oats, corn also weighs more per unit of volume. One coffee can full of corn has about 45% more calories than the same coffee can full of whole oats. So if a horse goes from one can of oats to one can of corn, his energy intake (from grain) is increased by about 45%. This has led to the idea that corn is a 'hotter' feed than oats. Actually, because of the higher fiber level in oats, oats produce more internal heat during digestion than corn."

Davison cautions that although corn or oats alone provide adequate calories, they do not offer adequate protein, vitamin, and mineral intake. Horses do better, winter and summer, on a high-quality, balanced diet of good-quality hay and a high-quality, fortified commercial feed.

Rice is Nice

Rice bran can also be added into the winter diet, says Williams. "Rice bran is beneficial to the horse that could use a little extra weight, or is still in training, because it adds energy in the form of fat and extra fiber to the diet to increase heat of fermentation. Rice bran is very palatable, so it will also stimulate a picky horse to eat and will increase the energy density of the diet."

Winter Outerwear

Because the horse's body condition affects the extent to which horses can deal with severe weather, it's important that horses come into winter carrying extra condition. It's a little more difficult for some horses to gain weight and create additional heat-producing energy at the same time.

"Additional body fat serves as insulation and energy reserves in times when the thermometer dips below the critical temperature," Davison says. "But once cold weather sets in, it is difficult to put weight on horses. Thin horses get colder and use so much energy trying to stay warm; there often aren't enough calories left for weight gain. Young horses and broodmares in late gestation may not be able to consume enough of a high-roughage diet, such as hay, due to restrictions in digestive system capacity."

Start increasing the hay in the diet when the pastures start to decline in the fall, Williams suggests. "You could start supplementing with other things such as rice bran, multi-vitamins, soybean meal, etc., only if necessary and when the temperatures start fluctuating around 30°F or when nights start freezing."

If your horse isn't in good body condition and needs to gain 50 pounds or more for winter, you can safely feed him an extra five pounds of hay per day, Davison says. "Just calculate how much he needs to gain and how many days you need to achieve that gain."

"It takes roughly 4,000 calories above maintenance to gain one pound," she states. "With most hays having 800 to 900 calories per pound, an extra five pounds of hay above the amount that maintains his current weight would allow him to gain one pound per day, so it would take 50 days to gain 50 pounds. Due to the calorie density, it would only take an additional 2.2-2.6 pounds per day of a feed like Purina Ultium, Strategy, or Omolene 200 to achieve the 4,000 calories needed per day. Again, this is in addition to the amount taken in to maintain current condition."

Keep in mind that water is an essential nutrient, too, and with increased amounts of hay in the diet, an increase in water consumption is vital for good health. Explains Davison, "Mature horses in temperate climates normally drink from five to eight gallons of water per day. With increased amounts of hay in the diet, water consumption rises to nine or 10 gallons of water per day. Increased hay intake combined with decreased water intake can potentially lead to impaction colic."

Because many horses drink less when their water is cold, keep your horse's water supply heated to 45°F to insure adequate intake and add one or two ounces of salt to his feed to stimulate water consumption, Davison advises.

If supplying water from unheated sources, break the ice at least twice a day and, in the case of buckets, replace icy water with more tepid water at least twice a day, adds Williams.

Four Myths

Among the many suggestions for providing additional nutritional winter support are a number of popular notions that aren't particularly beneficial:

1) "The number one myth is the benefits of hot bran mashes," says Williams. "Wheat bran does not serve as a laxative, nor does it keep the horse warm. Bran mash is what we, as nutritionists, call a 'comfort food.' It makes the owner feel better! Although it is neither harmful nor helpful to your horse, do not make a daily practice of this as wheat bran is not nutritionally balanced for horses and may throw off the mineral ratios of their normal ration."

2) You need to add digestive aids/anti-colic supplements for increasing digestion and reducing colic risk. "These products usually consist of some sort of probiotic or yeast culture, which has never been found to increase digestion in a healthy horse," states Williams. "However, if you have a horse that is having digestive problems or illness during the winter (or any other time), these products could be beneficial. As for anti-colic supplements, usually the problem in the winter is with a decreased water intake, and that can only be cured by increasing their water intake!"

3) Hoof supplements for winter-dry hooves. "Hooves may be brittle or crack from the cold, dry climate in the winter," notes Williams. "But hoof supplements will not help: Biotin and other hoof supplements work from the coronet band down and usually take six to 12 months to have any effect. If you are trying to treat a brittle, cracked hoof due to weather conditions, you need to apply something topically. It is best to talk to your farrier about what product would be best."

4) Calming aids or B-vitamins have no research support as to whether they calm a nervous horse, but the theory is there, Williams states. "If you've tried them and they seem to work, go head and use them. Some horses get very nervous if stalled for a long period of time (for example, in bad weather when they can't go outside), and if your horse responds to these supplements, they may not be a bad idea. B-vitamins are water-soluble, so if your horse has too much, he will just get rid of what isn't needed in the urine. The only thing you would be hurting is your pocketbook."

Take-Home Message

You should monitor your horse's body condition year-round, but it's especially important to do so before harsh weather arrives. "You can determine if your horse needs extra energy by checking for decreased body weight and body condition," advises Williams. "Make sure you feel through the heavy hair coat. Do you feel the ribs easily? If so, they need more energy. Are they shivering a lot? If so, they need more energy! Shivering helps them thermo-regulate, but they require energy to do so."

Don't wait until the temperatures plummet to zero degrees or the snow drifts three feet high: Start your winter nutrition program early and give your horse sufficient time to build up the reserves he needs to see him through the winter. 


The extra stall time that often occurs in winter can create another situation in which extra nutrients are needed. "A horse that is stalled continuously or for a long period of time may become extremely stressed," warns Carey A. Williams, PhD (equine nutrition), equine extension specialist at Rutgers University's Equine Science Center. "The stressed horse will have a decreased immune function and/or potentially develop gastric ulcers."

Decrease the risk of ulcers by keeping your stalled horse supplied with hay at all times. Having a full stomach will help buffer the stomach acid that is produced continuously. Minimize stress and help immune function by providing a vitamin E supplement (around 1,000 IU/day). However, watch the selenium level in the supplement; it is better to just find a pure vitamin E product to avoid any toxicity problems with the selenium.
--Marcia King

About the Author

Marcia King

Marcia King is an award-winning freelance writer based in Ohio who specializes in equine, canine, and feline veterinary topics. She's schooled in hunt seat, dressage, and Western pleasure.

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