Unexplained weight loss in your horse is a cause for concern for any horse owner. Luckily, many causes of weight loss are straightforward to diagnose and address.

If your horse is losing body condition, it could indicate an undiagnosed medical issue or it may simply indicate that your current feeding and management program is no longer working for your horse.

Older horses and horses affected by chronic disease are more prone to weight loss than healthy horses. [3][4][5] Horses also lose weight when exposed to extreme weather or when fed a diet that does not provide sufficient dietary energy to match their needs.

Other underlying issues that can lead to weight loss include digestive issues, dental disease, and social dynamics within a herd.

In this article, we will review some of the top reasons why your horse may be losing weight and suggest management strategies to support healthy weight maintenance. We will also discuss how to feed a horse to promote weight gain.

Diagnosing Weight Loss in Horses

Numerous factors can result in weight loss in horses, a commonly encountered issue in equine veterinary practice. [1] Weight loss occurs when a greater amount of energy is expended than received through the diet.

Horses naturally see their bodyweight fluctuate over the course of a year, typically losing weight in the cold winter months and gaining it back during the summer.

A temporary loss of body condition may also occur during pregnancy, lactation, and when performance demands are increased during competition periods. [2]

But if your horse is losing weight for an unexplained reason, it may be time for veterinary assessment.

A thorough evaluation of diet, management strategies, and health status is necessary to investigate the cause of weight loss in your horse. Your veterinarian will help you diagnose causes of weight loss based on:

Clinical Examination

A clinical examination is needed to determine if weight loss is occurring due to malnutrition or disease.

During a clinical exam, your horse’s body condition score (BCS) will be assessed. BCS is a measurement of the amount of subcutaneous fat tissue a horse has.

A thorough dental examination is needed to determine whether the horse is physically capable of eating the feed provided to them.

Digestion begins in the mouth with mastication (chewing) of feed. Horses with poor dentition may not consume adequate amounts of feed or may not be able to derive enough energy from the feed they consume.

Laboratory Testing

Blood and fecal testing may be completed to determine if your horse is losing weight due to an underlying health problem.

Your veterinarian may test for issues such as: [2]

  • Liver or kidney malfunction
  • Evidence of inflammation or infection
  • Gastrointestinal abnormalities
  • Internal parasites
  • Hormonal imbalances associated with conditions including pituitary pars intermedia dysfunction (PPID)

Advanced Diagnostics

Further diagnostic tests including rectal palpation, gastroscopy, thoracic and abdominal ultrasound, and biopsies may be used to determine the reason(s) for weight loss. [2]

Clinical Signs of Weight Loss

Common signs of weight loss include: [2]

  • Visible ribs and backbone
  • Bony projections present (in emaciated horses)
  • Lethargic behavior and poor performance in combination with weight loss
  • Exercise intolerance