Being underweight could have several causes. Just like being overweight, it firstly and foremostly has to do with the amount of energy that the horse receives in their diet. The overweight horse takes in more energy than they use, with the underweight horse it is just the other way around. The horse does not receive enough or poor quality food, causing their weight to drop. 

A horse’s energy needs may vary for several reasons. For example, if a mare is lactating, she has a higher energy need. If the diet is not adjusted then the weight of the mare may drop. The same goes for young horses that are growing. 

There may also be medical causes for being underweight. The horse may have a certain disease or condition, recovering from this can cost a lot of energy, causing them to lose weight. It may also cause digestion to function less optimally and food to be digested incorrectly. There could also be a worm infection, of which weight loss is one of the symptoms. In addition, depending on the type of worms, the horse may suffer from diarrhea, colic, loss of appetite, poor growth (in foals and young horses) and a poor coat. Bad teeth is another reason why the horse might not be getting enough food and/or the food is not properly digested, resulting in weight loss. 

If there is no medical cause, the horse may also lose weight due to (too much) stress. A horse can experience stress from their living environment if their natural needs are not met. It is also possible that the horse experiences too much stress during training. In addition to losing weight, stress can also cause other health problems, such as gastric ulcers or heart problems. 

Consequences of being underweight 

Being underweight can cause the horse’s general condition to deteriorate and they may become listless. The moment a horse receives too little energy through their diet, they will use their fat reserves. This eventually causes the bones to become visible. In very extreme cases, where the horse has used up all their fat reserves, other tissues are affected such as muscles, liver, kidneys, heart and the nervous system. At some point, all organs are affected and the animal may eventually die. 

Recognizing underweight 

As with overweight, it is important to keep a close eye on your horse’s condition. You can do this by regularly doing a Body Condition Score (BCS) of your horse. It can give you an indication of whether your horse is at a healthy weight at that moment. Keep in mind the differences in breed, conformation and age. There is serious underweight if the horse’s muscle tissue is minimal. The ribs and pelvis are clearly visible and the neck is sunken. When standing behind the horse, the spine is the highest point and the tail is sunken. If the horse suffers from underweight, the skin is still supple, but in extreme cases the skin is pulled taut. 

Tips for putting on weight 

It is important to find out what is causing your horse’s underweight. Have your vet examine the horse to rule out any illnesses and conditions. Also ask your vet or equine dentist to check your horse’s teeth. Is there no medical cause? Then it is important to take a good look at your diet and training. Lean horses have a higher protein requirement. Provide an appropriate diet that matches your horse’s energy and protein needs. The horse should be fed plenty of good quality roughage. By doing a roughage analysis you can see how much energy and protein is in your roughage. In addition, it would be nice if the horse has access to grazing all day, as grass contains more energy and protein than hay or haylage. You can add vegetable oil to the concentrate, or opt for a concentrate with a higher fat content. 

For pregnant and lactating mares there are special mare pellets that better suits the needs of the mare. A foal pellet has also been developed for foals. Do you have an older horse that has problems with their teeth, for example? Be sure to offer them easily digestible food. Wet food, such as beetroot pulp or mash, can help them gain enough nutrients. 

Be careful not to let a lean horse gain a lot of weight in a short period of time. Rapid weight gain puts the horse at several health risks, for instance increasing the chance of laminitis. Therefore ensure a gradual increase by adjusting the diet gradually.