Although there are certainly horses that are too fat, a common issue is horses need help maintaining weight.

The reasons may vary, but veterinarians routinely see equine clients that are thinner than they should be, observes Armon Blair, DVM, a veterinarian with Ocala Equine Hospital in the densely horse-populated area of Ocala, Florida.

The most typical classes of underweight horses Blair sees are senior horses and lactating mares.  

When a client calls Dr. Blair with concerns that their horse is too thin, he asks several questions upon examining the animal which should always be considered if a horse isn't holding weight:

• How old is the horse?
• What type of hay and grain are you feeding?
• When was the last time his teeth were checked?
• What is your deworming program?

The answers to these questions help guide a veterinarian when planning the best way to help a horse achieve and maintain optimal weight.

More protein or calories?

There are many different reasons a horse can become  thin. For starters, observing body condition may give an indication of what your horse is lacking.

As Blair explains, if a horse's ribs are showing, he generally needs more calories.

When muscle mass is depleted so that the top line is more prominent than it should be, this typically indicates that the horse needs more protein in the diet.

When a horse is both ribby and has lost muscle mass, this is a clear sign the horse needs more calories and more protein.

Blair adds that when a horse weighs less than he should and also has a poor, dull hair coat, this is a reason for concern. It could indicate an underlying health issue, such as parasites, or it could also mean the feed he is eating is of poor quality.

How much weight is needed?

If you have concerns that your horse is too thin, it's a smart idea to have your veterinarian do an assessment. Once he or she rules out any health issues, you can come up with a plan together to help the horse achieve and maintain his optimal weight.

The Henneke Body Condition score chart is a helpful tool that is widely used to evaluate a horse's physical condition. To learn how to use the system and what each body score looks like, simply do an internet search for "Henneke Body Condition Scoring System.”

For the average, middle-aged horse (not a pregnant mare or a highly fit equine athlete), a body condition score of 5 (considered "moderate") on the Henneke system generally means the horse is at a good weight. If you're looking for a range, it would be a body condition score of 4 to 6, not thinner or heavier.

With a score of 5 on the Henneke system, ribs cannot be seen but you can easily feel them when you run your hand along the horse's sides.

"A good rule of thumb is that you should always be able to feel the ribs even if you can't see them," says Blair.

Unless you have a livestock scale handy--which most farms don't­­ – use a weight tape to gauge your horse's current weight. Measure around the heart girth according to tape directions to get the most accurate weight.

Using this information, your veterinarian can determine approximately how much weight the horse needs and suggest a feeding program to safely achieve and maintain that weight.

If there are any conditions that need to be addressed, such as dental work or deworming, see that these are done promptly.

Start with forage

Although horse owners often think more grain is needed when a horse is too thin, Blair reminds them that high quality forage (pasture and/or hay) should always be the foundation of every equine nutrition program.

His top recommendation for most horses needing more pounds would be an alfalfa-grass mixed hay, such as alfalfa-timothy or alfalfa-orchard grass. 

If increasing the quality and amount of forage isn't sufficient for the horse to achieve and maintain optimal weight, the horse may need more of or a different type of concentrate ("grain").

Consider your concentrate

Blair urges owners to consider the type of concentrate not just the amount they're feeding. He strongly recommends using a name brand commercial equine feed designed for your horse's use and class, such as growth, broodmare, performance, maintenance or senior.

For example, nursing mares, growing horses, hard-working horses and seniors require different feeds targeted to their specific nutrient demands.

"With nutrition, you get what you pay for, and by all means, use feed designed for horses, not a general livestock feed," advises Blair.

He points out that feed intended for cattle can contain ingredients toxic to horses, so it's important to use balanced commercial feeds formulated for equines.

Check the amount

A common mistake horse owners make is feeding by the scoop, instead of actually weighing the feed.

Read any feed bag label and you'll see the directions on how much to feed are given in pounds--not scoops.

"A scoop is not a scoop is not a scoop! Feed should be weighed," notes Blair, who says that many times owners think they are feeding more than they actually are.

A simple kitchen scale is inexpensive and should be in every barn. This allows you to know how many pounds of feed you're giving your horse. You can still put that feed in a scoop to dump it in the bucket or feed tub--just weigh it first!

Adding a fat supplement

If a person already has their horse on good forage and an appropriate concentrate, "fat is the next thing we go to as an additional source of calories. Fat is a very calorie-dense source of energy," says Blair.

Adding calories from fat rather than from starch (concentrate) is recommended for horses that tend to be more nervous or high-energy. Fat can also be a good way to help senior horses maintain weight.

All fat sources are not the same, however. Some horse owners add oil to their horse's grain when extra calories are needed, but that isn't always appetizing to the animal. When a calorie-dense option is needed, you will typically be better off feeding an extruded fat supplement, rather than just adding oil.

Fat provides calories and energy, but you also want to add a balance of protein, vitamins and minerals. A good fat supplement like Farnam^® Weight Builder™ Equine Weight Supplement can do this by providing additional nutrients.

Such a supplement will provide essential omega-3 fatty acids and is more palatable for the horse than oil alone.

Senior horse concerns

"Horses are like people in that some age better than others," says Blair.

In addition, he finds that many owners don't keep up with regular dental exams and a deworming program after a horse is retired and not being ridden routinely.

When called to a farm to assess a thin senior horse, Blair often finds that these horses have poor dental conditions. Teeth may be missing or molars may be so worn down that the horse can no longer properly chew hay.

If forage is not chewed properly, the horse's body won't absorb all the nutrients in it, and in addition, becomes less efficient. In both situations, it makes sense for the horse to be on a senior feed. Commercial feeds designed for senior horses are formulated to meet all nutrient requirements, even if horses cannot chew long-stemmed forage.

If your older horse can still eat hay, he won't need as much senior feed as a horse who is totally dependent on it for all his nutrition. Follow label directions and weigh the feed to be sure you are feeding the correct amount.

When switching to senior feed from another feed, do so gradually over the course of about a week's time to help avoid digestive upset.

How long will it take?

"Unless a horse has been starved, I tell people it can take several months to see a significant change in weight for the average horse, so you have to be patient," says Blair.

Just to go from a score of 4 to 5 on the Henneke Body Condition Scoring System, a horse needs about 45 to 50 more pounds. So, if a horse is too thin, say a body score of 3, he'll need about 100 more pounds to get up to a score of 5.

Keep in mind through all of this, though, that drastic diet changes can cause digestive upset, so it's safest to feed for slow accumulation of pounds. Your veterinarian can help you plan the best course of action. Blair explains that 90 days is a realistic time frame for a horse that needs about 100 more pounds.

Bottom line? If your horse has lost weight or is having trouble keeping it on, it's time to call your veterinarian.