Transitioning horses to a hay diet during the cold weather months may lead to deficiencies in key nutrients and a need for supplementation. Here’s how to advise your clients when it comes to winter feeding.

As nature slips toward dormancy in winter, hay becomes the forage of choice for most horses. Once fresh grass is cut, dried and stored as hay, however, its vitamin content, along with valuable Omega 3 fatty acids, dramatically decline, making supplementation necessary to fill in the nutritional gaps. Hay also has very little moisture compared to fresh pasture.

In other words, it takes more than hay to keep horses healthy during the colder months.  Even horses living in a milder southern climate without the blizzards of the north are impacted by weather changes in a variety of ways. Optimal nutritional planning will help your equine patients enjoy the season and emerge in good condition when spring arrives.

Shift slowly and check teeth

Any time the diet changes, it should be done gradually to allow the hindgut microbial population to adjust. This is also a great time to have your patients’ teeth checked for points that can make chewing painful. Hay is more difficult to chew and teeth need to be in top shape.

Vitamin D is key

Hay cannot compare to fresh grass when it comes to nutritive value. Once grass is cut, dried and stored, it begins to lose vitamins C, D and E, beta carotene (for vitamin A production), and Omega 3 fatty acids.

Normally, a horse produces vitamin D when exposed to sunlight. But spending more time indoors, combined with shorter daylight hours, can induce a vitamin D₃ deficiency, leaving bones, joints and muscles unprotected. When exposed to sunshine, 7-dehydrocholesterol in skin oils is converted to cholecalciferol, which is then converted in the liver and kidneys to vitamin D, known as 25-hydroxy-cholecalciferol, or D₃ for short. It’s a hormone, since it is produced in the kidneys, yet it has effects in the small intestine and bones. D₃ is critical for maintaining blood calcium, so the horse’s bones, joints and muscles function optimally.

• D₃ helps calcium absorption in the gut.
• If there is not enough calcium in the diet, D₃ triggers the bones to release calcium into the blood.
• D₃ prevents loss of calcium in the kidneys.

A half-hour to 90 minutes in the sun will give the average person all the daily vitamin D he/she needs. But it typically takes five to eight hours of exposure to ultraviolet light (which is still present, though to a lesser degree, on cloudy days) for horses to produce enough vitamin D. This increased time is due to many barriers including hair, blankets, fly sprays, coat conditioners and reduced body oils (if recently bathed).

Winter (with its blanketing and less sunlight), frequent bathing and an indoor lifestyle cause vitamin D deficiency, leading to reduced appetite, slowed growth, bone demineralization (leading to stress fractures and bone deformities), and poor muscle contraction. Therefore, a vitamin supplement, along with flaxseed meal or chia seeds (to provide Omega 3s), will fill in the nutritional gaps created by hay-only diets.

Consider alfalfa

Contrary to popular opinion, alfalfa it is not higher in sugar than grass hay. It is high in protein, but this is a good thing. At a moderate intake (approximately 10% to 30% of the total hay ration), it boosts the overall protein quality of the diet to keep a horse’s muscles, joints, feet, skin, hair and bones fed, as well as protect her blood and immune function. Alfalfa also serves as a stomach buffer against developing an ulcer, a common occurrence when a horse is stalled during the winter after being accustomed to fulltime turnout.

Hay should be offered free-choice

Cold weather increases the metabolic rate, which means horses need to burn more calories to maintain a normal internal body temperature and consistent weight. When hay is provided free-choice day and night, it simulates the horse’s natural need to graze. It allows her to consume the increased amounts she needs to help stay warm and account for this higher energy requirement. Free-choice is always best (regardless of the season or condition) because it allows the horse to self-regulate her intake and eat only what her body needs. Horses that experience an empty stomach between hay “meals” will eat their hay very quickly. Horses offered hay free-choice will learn there is always hay available, and will therefore eat more slowly and self-regulate their intake to eat only what they need to maintain condition. This lowers the risk of colic.

Concentrates for more calories

For many horses, hay will not provide enough calories to maintain normal body condition. A high-fat commercial feed is fine for healthy horses. For the easy keeper or insulin-resistant horse, avoid sweet feeds and those that contain oats or corn. Beet pulp, alfalfa pellets, or low starch commercial feeds are excellent alternatives. Fatty feeds such as rice bran, flaxseed meal, or chia seeds offer the most concentrated source of calories. Avoid corn or soybean oils, since they promote inflammation due to their high Omega 6 fatty acid content. When clients feed bran mashes, or any added feed, they should give it every day. Consistency will prevent colic. Keep in mind, however, that bran (rice or wheat are most common) is very high in phosphorus in relation to calcium. Therefore, advise clients to use a commercial product with added calcium, or to feed alfalfa to counteract the elevated phosphorus content.

Older horses need special attention

The older horse may need a joint supplement along with vitamin C for collagen production (the protein found in bones and joints), since less vitamin C is produced as horses age. For the hard keeper, clients should make sure there is no competition from younger, more aggressive horses for hay. Older horses should receive a senior feed, along with added flaxseed meal.

Other winter tips

• Water consumption needs to stay at optimal levels. Since most horses do not drink enough water when it is icy cold, it is best to use a heated water bucket to bring the water temperature up to 50ºF. Dehydration due to decreased water consumption is the main cause of colic during the winter. Snow is not a substitute for water.
• Use a prebiotic (fermentation product, not live microbes) or a potent probiotic (one that contains billions — 10⁹ — colony forming units) to keep the hindgut microbial population healthy. Boosting the health of bacterial flora living in the hindgut eases the transition from one form of forage (pasture) to another (hay).
• Don’t forget salt. Salt blocks, free-choice granulated salt, or two tablespoons of table salt added to the horse’s meals per day (divided between meals), will keep his body in proper water balance. Salt blocks are made for cattle with their scratchy tongues; horses’ tongues are smooth so they may avoid salt blocks because they can cause irritation. Clients can offer granulated salt, free-choice. They should start out with a small amount so the horse’s curiosity won’t result in him eating a big mouthful of salt. Once the horse sees it’s salt, the client can fill the container with enough to last a few days. A full-sized horse requires approximately two tablespoons (one ounce or 28 grams) of table salt per day, divided between meals.
• Clients should avoid blanketing their horses if at all possible. The winter coat is designed to keep the horse warm and regulate his internal body temperature. However, horses should have access to a shelter to get out of the wind, rain and heavy snow so their skin remains dry. Blankets flatten the coat, making it unable to protect the horse against extreme cold. If the horse is very thin, or clipped, and the client finds a blanket is necessary, have her check his condition each day to make certain he is not sweating.

Preventing colic when transitioning to hay

Because of the nutrient differences from grass, and because hay has very little moisture compared to fresh pasture, colic risk significantly increases in the winter months.

Colic is the number two killer of horses, number one being old age! Colic isn’t actually a disease; it’s a symptom of another problem. With increased hay consumption, impactions and excess gas production are the most common causes. Enteroliths (stones) are often seen in high alfalfa hay diets. And ulcers often develop when a horse is transferred from day-long turnout to longer periods of time in the stall. Following the feeding guidelines in this article will significantly lower the risk of colic.

Special keys to prevent colic:

• The client should offer hay 24/7 to keep the intestinal motility normal, prevent acid buildup, and protect the vital forage-digesting hindgut microbes.
• Make diet changes slowly.
• Offer a pre-biotic.
• Provide plenty of tepid water.
• Provide salt, which encourages drinking to prevent impactions.
• Limit winter stalling.
• Float teeth to prevent partially chewed hay, which can cause impactions throughout the digestive tract.
• Allow the horse to be a horse just as much during the winter as the rest of the year.
• Consider an intestinal soothing supplement, typically containing herbs such as chamomile and slippery elm, to ease digestive distress.

Quality of hay

Not all hay is alike. If clients have two months’ supply or more, it is worthwhile for them to have the hay analyzed for its sugar and starch content, as well as protein, minerals and selenium levels. Equi-Analytical Labs will offer a complete analysis at a nominal fee: visit  equi-analytical.com to learn more.