Whether it’s just a few mouthfuls of feed sitting in the bottom of your horse’s bucket or a whole ration untouched, discovering that your horse has suddenly lost his appetite is troubling—and it should be.

A horse doesn’t refuse to eat without a reason, and that reason could be serious and even life-threatening. If your horse has lost his appetite and is showing any signs of illness or distress—such as a fever, discolored gums or elevated heart rate—it’s cause for an immediate call to your veterinarian. Likewise, if you notice half-chewed feed or other evidence of tooth or oral issues, arrange for a dental checkup.

If, however, your horse seems physically fine, your first instinct may be to change his grain and whip up something “more interesting” in the feed room. But that’s not the best course of action, experts caution.

“There are a multitude of things people try, to get a horse to eat,” says Stephen Duren, PhD, founder of Performance Horse Nutrition, a consulting firm in Weiser, Idaho. “They start changing everything—feeding a different grain, or a different hay, or put molasses in the grain. Before I’d start trying all kinds of new things, if I had a horse that was eating well and suddenly stopped, I would first find out why he is not eating. I try to solve that issue first.”

Time to investigate

It might take a little bit of detective work to find the source of the problem. “A person needs to step back and look at this logically and work through a progression of possibilities, which includes medical problems, and if those are ruled out, look at feed quality, and then look at what else might have changed, such as the horse’s routine or exercise,” says Duren. “Stabling can be an issue if the horse’s routine has changed. I work through all of these possible issues before I think about changing a feed, especially if that feed at one point was being readily consumed by that horse.”

A variety of social and environmental factors can put a horse off his feed—and it may even be a problem with the quality of that bag of feed or bale of hay itself. To help you figure out which factors or combination of factors may be affecting your healthy horse’s appetite, we’ve presented three major areas of inquiry along with additional questions in a “decision tree” format.    Each answer will point you toward potential solutions. With luck, the problem will turn out to be something that is easy to fix.

Question 1: Is it the food?

A horse might reject hay or grain if it has a smell or texture he doesn’t like. “Horses are very adept at sensing when something is ‘off’ or different. It might smell different or taste different,” says Shannon Pratt Phillips, PhD, of North Carolina State University. “Their acute senses help them avoid consuming toxic plants; they can detect any subtle difference in the feed.”

Has only one horse lost his appetite or have several others in the barn?

If you find leftover feed or hay in one stall, check the other stalls and see if any other horses have also snubbed their food. “If all the horses stop eating you can assume it’s the feed,” says Phillips.

What to do:

Check the rest of the feed for debris, such as mice or snake carcasses that might have gotten caught up in the processing. Also look for wetness, mold or other contaminants that may be affecting the smell or taste. “Maybe you started feeding some hay that has weeds or mold in it,” says Duren. “Maybe the grain is old, or dried out, or insect infested. These can be reasons for a palatability issue and the horse stops eating.”

Additional quality checks

Also check the quality of any supplements you may have added to the rations.

If horses throughout the barn seem to be wasting a lot of hay, check your supply for palatability. Pick up and squeeze a handful: Any jabbing on your palm means your hay may be too “stemmy.” Less expensive hay may actually cost you more over the long run because your horses waste so much. Switching to a higher quality hay may be more cost-effective.

“Certain types of hay are much more palatable than others,” says Brian Nielsen, PhD, Dipl. ACAN, of Michigan State University. “Some years ago if a person asked my advice when they had trouble keeping weight on a horse, I would suggest grain and a high-fat diet because it’s more energy-dense and the horse doesn’t have to eat as much to get the necessary calories. What I’ve discovered is that if you just feed a high-quality hay diet, often with a fair bit of alfalfa, giving that horse as much good hay as he wants, it’s a rare horse that won’t eat an adequate amount.”

A more palatable hay may also save you money on other products. “I am always amazed at how some people are hesitant to increase the amount of hay they feed. Or change the type of hay, yet they are willing to spend a lot of money on grain or supplements,” Nielsen says, “whereas some good alfalfa hay may do the trick and get the horse eating better. It’s a simple fix. Often you just need to go back to the basics with these horses, which is good forage.”

Are you feeding from a new bale of hay or a new bag of your horse’s regular feed?

“Even if it’s only one horse in the barn or group that suddenly goes off feed, it might still be something in that horse’s food,” says Phillips.

What to do:

“I suggest taking that feed away and opening a different bag or bale, to see if there is something else the horse will eat,” says Phillips. “You hear stories of horses eating toxic feeds, or a situation where there has been a formulation error and too much vitamin D or something else is in that feed. There will always be some horses that eat it anyway and get sick, but there might be some that refuse to eat it. So my first thought would be to check the feed itself.”

If the horse readily eats the new feed or hay, set the old aside. “If you suspect that it’s the feed, take a sample, set it aside and have it checked,” Phillips adds. “You might send it off to a lab and see what might be wrong with it, if you think it might be a feed manufacturing error. If you suspect the feed, I advise not feeding it to any of the other horses.”

Have you added anything new to the ration?

Adding anything unusual to the ration, like a fat supplement or electrolytes, may put off a fussy eater.

What to do:

Try feeding the horse again, minus the suspect addition. If he eats, he just didn’t like the change. If this becomes a chronic problem, consider whether you may be contributing to your horse’s finicky attitude.

“The fussy eater might benefit from some diet manipulations,” says Duren. Adding a dollop of applesauce or molasses to the ration, for example, may encourage a horse to eat more readily. “However, when you start adding and subtracting diet ingredients, this in itself encourages a horse to be picky. You are giving him many choices. He ultimately is going to eat what he likes best and start being fussy about some of the other things. We see this a lot with racehorses when people hand mix the ingredients of the diet. They ultimately have horses that become more picky and fussy about what they eat,” he says.

“Horses do better with a consistent diet that contains fresh, palatable ingredients, and you don’t alter it,” Duren says. “Yet there are some people who think a horse would get tired of eating the same thing every day. Horses are not like people, however, who get bored with the same menu and want to try new things. If a horse’s food is nutritious and palatable he will generally keep eating it.”

Will the horse eat something different?

Few healthy horses will pass up the opportunity to graze on green grass or scarf down a treat. “Unless a horse has dental problems or other issues that hinder grazing, if he is out at pasture on lush grass, he will readily gain weight,” says Nielsen. “This is the best way to kick-start appetite and put weight on horses that need to eat more.”

What to do:

If the horse turns up his nose at his usual rations, offer him a treat or something else that he is usually eager to eat. “Will he still eat an apple or a carrot or something you know he likes, or some green grass?” Phillips asks. “If he doesn’t want to eat that, something is off with the horse himself. This is a way to determine whether it’s something in the food or some problem the horse has.”

But don’t go too far afield: “You don’t want to offer something so different that he doesn’t want to try it, or something that might be too big a change that could affect the hindgut’s microbial population,” Phillips says. “If there is already something abnormal going on, this might make it even worse.”

If you can’t tempt your horse with treats he typically enjoys, call your veterinarian.

Question 2. Is it a “social” issue?

Herd dynamics, social stresses and other issues can affect behavior at mealtime. If you provide ample hay for horses on full turnout, yet some still seem to be getting too thin, you may need to spend some time observing your horses to see what is actually happening in the field. Also consider whether other changes in a horse’s life may be stressing him.

“Sometimes simple management changes can help encourage a reluc-tant eater, though this requires pay- ing attention to what’s happening at mealtime,” says Nielsen. “You might see a thin horse out in the group and wonder why he is thinner than the others but if you pay attention to the social hierarchy and interac- tions this might give you a clue.”

Are all of the horses able to access hay at will?

Dominant horses may sometimes bully other herd members away from the food sources, and the more timid ones may not get enough. “The dominant horse stays fat because it gets first dibs on the feed, and the timid horse hangs back, not wanting to get kicked or beat on,” says Nielsen. “The subordinate horse may sacrifice eating, just trying to survive.”

Older horses who have dropped in the pecking order may be particularly vulnerable to being pushed away from the feeder by younger pasturemates. Those with arthritis or other lameness issues may not be able to move quickly enough to defend themselves, and they may feel safer staying farther away.

What to do:

Instead of placing all of the hay in one large feeder, spread out smaller amounts around the pasture. One option would be to place smaller feeders—preferably one or two more than the total number of horses in your herd—at various locations around the field. That way, a horse who is pushed away from one feeder can always go to another, and as a bonus, all of the horses will be encouraged to spend more time walking.

Another option would be to bring the horses into separate pens at mealtimes so they can all eat in peace.

Does your horse live alone?

In a herd, there is safety in numbers when some members can remain alert for predators while others graze or sleep. A horse living alone—particularly one who is used to having company—may be nervous about spending too much time with his head down grazing. “I’ve seen this many times,” says Nielsen. “Horses are social animals. If they don’t have another horse to hang out with, they may not eat as well. They are social eaters and eat better if another horse is there.”

There is also a competition factor, he says: “If there are a lot of horses, or huge inequality on the social scale—with some horses chasing others away from the feed—this can stimulate a normal, healthy horse to try harder to get his share. It’s like kids growing up in some families; if you didn’t eat at the dinner table you were going to go hungry. So you sat right down and started eating before all the food was gone. Horses in groups are often competitive eaters, wanting to get their food so they won’t miss out.”

What to do:

If you can manage the care and feeding of another horse, finding a compatible friend for your solo one may be the best option. A Miniature Horse, donkey or smaller pony may also fill the bill. Some horses are also able to bond with sheep, goats or other livestock. Be sure you understand the unique needs for the care and feeding of any other species you might bring home.

Has the environment changed?

Any disruptions in a horse’s life can sometimes cause him to stop eating. Has your horse just lost his best buddy, or does he seem to dislike a new addition to the herd? Has he recently been moved to a new barn, or has his care routine changed? “We’ve seen horses that will eat in a particular stall, yet won’t eat in other stalls,” says Duren. “It has to do with the environment, the horses next to them, and so on.”

Stress of any kind may affect a horse’s appetite. “This could be transport stress, overwork or some other kind of stress,” Phillips says. “It may be a combination of stresses.”

What to do:

“When horses travel, especially when they are on a flight or hauled long distance, it may take a day or two for them to recover from that stress and they might be off feed until they get re-settled,” Phillips says. “You don’t want the horse to not eat during that time, however, because this would be unhealthy for the digestive tract. You want to do whatever you can during that time to get them to eat. This might mean offering soaked hay or soaked hay cubes, perhaps with a little molasses added to the soaked cubes to make them even more palatable.”

If the change in a horse’s life cannot be simply undone—such as moving him back to his usual stall—then just keep tempting him. Most horses will begin to eat again once they start settling into the new routine.

Question 3. Could it be overwork?

When other factors have been ruled out, says Duren, “I look at the next possibility: What have I done with that horse from a work/training standpoint? Even if I’ve been training or riding the same way all summer, perhaps the horse has finally gotten tired or burned out on the work he’s been doing, and then he doesn’t feel like eating. This is a documented response called ‘overtraining syndrome.’”

Is the horse in training for a demanding sport, such as endurance or eventing?

“We might say that a racehorse has gone ‘track sour’ when it stops eating,” says Nielsen. “When I was an exercise rider, we’d often come back the next day after a horse raced and the first thing we’d ask is how that horse was eating. Some of those horses go off feed, and there are several reasons why a hard-working horse might have reduced appetite.”

What to do:

If the horse goes off his feed the day after a particularly hard or long workout, try giving him a day or two off. Chances are, he will start eating again.

“It’s a bigger issue when you have been steadily campaigning too hard,” says Duren. “Horses reach peak fitness and then go past that peak and start eating less. Research in laboratory animals shows that if you increase their exercise it initially builds appetite, and then when you get to a certain threshold and get into an overtraining situation, their appetite drops off. They start down a path of decreased intake and increased weight loss and decreased performance.”

If refusing food becomes a chronic problem in your equine athlete, it might be a good idea to consult with a veterinarian or trainer who is experienced with your sport to recommend a schedule that provides a better balance of work and rest. Your horse may need some time off work, followed by a more gradual return to training. “Rest at the right time becomes crucial to prevent this type of over-conditioning,” Duren says. “Timing of work and rest is important in keeping a good appetite, as well.”

Is your horse’s diet comparatively high in grain?

Most hard-working equine athletes can’t get all of the calories they need from forage alone, so their diets are supplemented with grains or other concentrated feeds. But this can alter the chemical balance within the intestinal tract. “Many hard-working horses are on a high-grain diet rather than a high-forage diet, so one of the things we’ll often see is an increase in propionate formation,” says Nielsen, noting that propionate is a short-chain fatty acid linked to metabolic function. “When there is too much propionate accumulation, it can depress appetite.”

A horse who is off his feed may be more inclined to eat grain rather than hay because grain tastes good, but if he eats more and more grain and less hay, this can become a vicious cycle, depressing his appetite even more. A high-starch diet also puts a horse at risk of colic and laminitis, says Nielsen: “If some of the starch gets into the hindgut, it creates some changes that can be detrimental.”

What to do:

Consult with your veterinarian or an equine nutritionist before making any significant changes to your horse’s diet. Recommendations may include adjusting your horse’s feeding schedule to provide his ration in fewer, smaller portions spread throughout the day, or maybe even switching to a different feed that is better formulated to meet his caloric and nutritional needs.

A hard-working athlete may benefit from additional vitamins. “Rarely do I recommend supplementing with vitamins because the average horse generally doesn’t need any extra,” says Nielsen. “Once in a while, however, additional vitamins might make sense. With the high-grain diet, more propionate is produced, and this decreases appetite. The good news is that vitamin B12 can play a role in changing this. You can add vitamin B12 to the diet with a supplement or you can inject it to resolve this problem.”

Thiamine (vitamin B1) may also be helpful. “This vitamin is beneficial for energy metabolism,” says Nielsen. “Normally the microbes in the hindgut manufacture enough of this vitamin, but in hard-working horses with a high energy demand, sometimes they don’t seem to be able to make enough thiamine. The lack of thiamine also depresses appetite. There are various ways to provide thiamine or B vitamins in general.”

“Traditional” remedies

Some “traditional” remedies may also work. “In earlier days it was common for trainers to add a bottle of beer to the horse’s feed to stimulate appetite, and it seemed to help,” Nielsen says. “What it may have done was introduce some B vitamins. Brewer’s yeast will do the same.”

These days, however, Nielsen recommends more conventional methods of administering B vitamins. “You can provide vitamins in the diet, but an injection is quicker, easier and less expensive,” he says. “There have been a number of times when horses have gone off feed and I recommended injectable B vitamins, and it helped. I was amazed at how much it seemed to kick-start their appetite, especially in hard-working horses.”

Figuring out what is going wrong when a horse isn’t eating is easier when you are familiar with his normal behavior. It’s a good idea to spend some time now and then watching your horse eat. “Rather than just giving him the feed and leaving, I try to stay there a few moments and watch him, even when there is nothing wrong,” says Phillips. “Then if something is wrong, I’d notice it.”

With some luck, and quick action, you’ll be able to get your horse back into a healthy feeding routine in no time.