A horse’s nutrition needs can change significantly as the seasons come and go. This is due to higher temperatures, as well as the type of nutrition a horse is getting — and needs­ — during the summer vs. the winter months.

When the lush grass is no longer available and temperatures plummet, a horse’s dietary needs are affected.

Winter’s Effect on Dietary Needs

The switch from pasture grass to hay is often the prime factor leading to loss of body condition during the winter.

“Hay is typically less calorie-dense than pasture grass,” explains Scott Gravlee, DVM, CNS, and equine nutrition consultant at Life Data Labs. “The cold weather also increases a horse’s metabolic demands to stay warm. If there are insufficient calories in the diet, horses will burn their fat reserves to satisfy the increased calorie demand.”

During summer months, carotene is found in fresh pasture grass and converted to retinol in the horse’s digestive tract.

“Retinol is the active form of vitamin A,” Gravlee says. “The carotene content of hay decreases over 50% within a few days following harvest, while other vitamins, such as vitamin E, deteriorate at rates as high as 7-10% per month.”

In addition, the lower temperatures also play a role in how a horse’s dietary needs change in the winter. The horse has a thermoneutral zone, where heat produced and heat lost are balanced.

“When horses have a chance to acclimate, the lower critical temperature (LCT) for mature horses when dry with little wind is 10 degrees Fahrenheit,” says Richard G. Godbee, Ph.D., PAS, Dipl ACAS-Nutrition. “When the horse is wet, the LCT is 59 degrees Fahrenheit — substantially higher.”

As a result, a horse’s energy intake must be increased to account for the effect that colder temperatures have on energy requirements.

“For every 1 degree Fahrenheit decrease in LCT, the digestible energy requirement for maintenance is increased by 1.4%,” Godbee adds. “This is to help meet the demands winter temperatures have on digestible energy requirements.”

There are several things to consider when trying to safely accomplish this — increasing the total feed intake or changing the type of feed being fed.

“Feeding more hay will increase the heat increment, which helps the horse stay warm,” Godbee explains. “Feeding more grain or a concentrate is not a good alternative, though, since it does not increase the heat increment and may result in digestive upset. Protein, vitamins and mineral intake, relative to ambient temperature, are minimally impacted.”

While it’s also easy to consider a horse’s hydration in the summer, it's equally important they stay hydrated in the winter.

“Water is still the most critical nutrient required by the horse regardless of the time of year,” he says. “They still require 8-10 gallons of water per day. Snow as a water source is typically a very poor choice. Usually, the water content is low and the intake will lower the core body temperature — not the direction wanted. A decrease in water intake will also result in a decrease in feed intake.”

Horses tend to drink less when their water is cold, so keeping the buckets free of ice and as warm as possible is important.

Preventing Problems

Poor nutrition negatively impacts every cell in the horse’s body. When it comes to feeding horses both in the winter and throughout the year, forage is key.

“Feeding a good grade of hay or roughage in sufficient quantity is the best source of calories,” Gravlee says. “A horse will normally consume 2-2.5% of their body weight on ‘dry matter basis’ of hay or pasture grass per day. Hay typically dries to about 15% moisture while in covered storage; therefore, a 1,000-pound horse would consume up to 25 lbs. of hay during a day. Free choice hay is ideal so that the horse constantly nibbles. For obese horses, try a slow feeder hay net. However, horses that compete or perform regular work and are not obese may need additional calories for energy.”

It's important to consider the horse’s weight going into winter. The first step in determining the adequacy of the horse’s diet is to do some basic arithmetic.

“Calculate the amount of energy, protein, minerals and vitamins the diet supplies relative to the requirement for these nutrients based on the horse’s production and use,” Godbee explains. “Understanding and using the Body Condition Scores (BCS) to help determine if the horse is under condition going into winter is important. A BCS of 6 or 7 is preferable, as this indicates more body fat stored that can supply additional energy, if needed, and act as an insulator.”

Signs of vitamin A deficiency include poor hoof wall quality, as well as hair growth from the hoof wall. Life Data labs

If the horse needs calories in addition to quality free-choice hay to maintain body condition, whole oats are an excellent source of supplemental calories. The starch in oats is highly digestible and is quickly broken down into sugars in the small intestines and absorbed.

“Another good source of calories is beet pulp or copra (coconut pulp),” Gravlee says. “Beet pulp and copra are digested by hindgut microbes into beneficial vitamins, amino acids and volatile fatty acids (VFAs). VFAs are efficiently utilized as a calorie source. Beet pulp or copra increases the caloric density of the diet without the formation of glucose and is therefore ideal for starch-sensitive, insulin-resistant horses. An added benefit is that the digestible fiber of beet pulp and copra also provides heat from the hindgut fermentation process. Vegetable oil added to the diet also provides calories produced by hindgut microbes in the form of volatile fatty acids.”

However, increasing compounded or all-in-one feeds to help a hard keeper gain weight is often counterproductive.

“When feeding compounded feeds, nutrient intake is regulated by the amount of feed intake because the fortified nutrients and calories are tied together and cannot be separated,” he says. “Increasing the feeding level of a compound feed to increase calorie intake is in effect ‘force feeding’ the fortified nutrients and often results in over-supplementation. Nervousness, metabolic problems and loss of body condition are associated with poor quality diets and over-supplementation.”

How Farriers Can Help

When nutrition is poor overall, the hooves are one of the first places where it’s noticed. Farriers are in a great position to help horse owners learn more about hoof care, regardless of the season, but especially when it comes to how nutrition in the winter affects their horses’ hooves. Since farriers see horses on a routine schedule, they can spot small issues and help correct them before they become large issues.

When it comes to hooves, vitamin A deficiency can affect horses significantly in the winter — especially horses eating primarily hay as forage.

“Vitamin A losses can be as high as 75% during the curing phase of hay production,” Godbee says. “Storage can add another 5-10% loss per month, depending on the storage techniques. Vitamin A is essential in promoting keratin synthesis with a direct impact on the stratum medium in the hoof wall. It’s also important in collagen synthesis, needed for the suspensory apparatus. There are reports in the literature that up to 50% of the vitamin E in grasses may be lost during curing. Vitamin E is an antioxidant that protects against oxidative stress, protecting keratinocytes from cell damage. It’s also important in membrane integrity.”

Hay and pasture balancers can provide nutrients such as vitamin A and vitamin E that are often lacking in stored hay.

“Vitamin A deficiency in a horse’s diet can cause poor hoof quality,” Gravlee adds. “The hoof wall may become shelly and flaky, and the appearance of the hair-like projections growing around the coronet band from the hoof wall can be visible.”

A hoof supplement can also help with these deficiencies. Some of the major things to look for in a quality supplement are a protein source like soybean meal, biotin, chelated trace minerals, zinc, copper, ground flax seed or flax oil to supply essential fatty acids and added amino acids, methionine and lysine. Added vitamins C, A and E are also beneficial.

“Adding in a quality hoof supplement may also help improve the density of the hoof wall, and thereby help reduce the potential long-term effects of laminitis if a bout should occur,” Gravlee explains. “Healthy hooves with dense hoof walls are more resilient to invasion by ‘hoof-eating’ bacteria and fungi, thereby decreasing the incidence of white line disease and crumbling hoof walls.”

Be sure any supplement is made by a reputable manufacturer and remember it takes time to see whether a product is working — sometimes 9 months or more. Because of this, farriers can help their clients by reminding them to start thinking about winter nutrition long before the first snowfall. Farriers will also have more hoof to work with when the horse is given an effective hoof supplement.

“If needed,” Godbee says, “contact an equine nutritionist for ration evaluation.”