Horse Side Vet Guide ®

Equine Health Resource

Not Eating, Loss of Appetite, Not Hungry

Code Red - Call Your Vet Immediately, Even Outside Business Hours

Code Orange - Call Your Vet at Their First Available Office Hours

Code Red - Call Your Vet Immediately, Even Outside Business Hours

  • If this behavior persists without an apparent cause.
  • If the results of the Whole Horse Exam (WHE) in the resting horse indicate fever (Temp >101F/38.3C) or heart rate greater than 48 BPM.
  • The feed is the same as it has been. Nothing has changed.

Code Orange - Call Your Vet at Their First Available Office Hours

  • If the results of the Whole Horse Exam (WHE) suggest the horse is otherwise normal.
  • A change in the feed could explain the horse's lack of appetite.

Horses are usually aggressive eaters. When they show less or no interest in feed, it should be a warning sign. Appetite is regulated in all mammals by the hypothalamus part of the brain. Disease processes of different kinds create chemical signals that affect the brain and may decrease appetite. Horses experiencing abdominal pain (colic) are oftentimes (but not always) reluctant to eat.

Horses with pain in their mouth will usually try to eat but have difficulty. Those with pain in the throat and esophagus will chew feed but may have difficulty swallowing. Horses that suddenly experience choke or pain while eating may immediately stop and walk away from feed.

Any time a hay or feed is changed, there is a chance that a horse will be reluctant to eat the new feed, until they become hungry enough to begin eating again. Horses that have recently been given oral medications may not eat until they rid their mouth of the taste of the medication.

It is important to try to determine whether your horse has truly lost their appetite, or is hungry but prevented from eating by something (pain, mechanical obstacle, etc…).


Assess your horse’s general health using the Whole Horse Exam (WHE), and try to determine whether your horse is having difficulty chewing or swallowing. In some cases, it may be helpful to assess their mouth (wear gloves). Offer your horse a small amount of feed and watch what they do. If you recently switched feeds, offer the previous one that they may prefer.

If you cannot clearly attribute this behavior to a simple management or feed change, or if you notice any other abnormal behavior, call your vet to discuss your findings and concerns.


Your vet will take a careful history, considering the above factors. A physical exam offers clues to the body systems that might be involved. Often, laboratory work is needed to help rule out more subtle causes of inappetence

Identify or Rule-Out Possible CausesDIAGNOSES

Within Normal Limits, Normal for this Horse
Large Colon Impaction, Pelvic Flexure Impaction
Retained Placenta
Colic, Undiagnosed Conditions Causing
Salmonella Colitis (in Growing Foal or Adult)
Colic, Gas, Large Colon Tympany
Duodenitis-Proximal Jejunitis, DPJ
Hyperlipemia, Lipemia
Colic, Simple Intestinal Gas or Spasm
Intra-Muscular Injection Site Reaction
Equine Gastric Ulcer Syndrome, EGUS (in Adult)
Liver Failure, Generally
Foreign Body in Mouth
Pigeon Fever
Equine Influenza, EI
Enteroliths, Intestinal Stones
Equine Granulocytic Ehrlichiosis, EGE
Small Intestinal Strangulation, Strangulation by a Pedunculated Lipoma
Renal Tubular Acidosis, RTA
Acute Systemic Disease, Generally
Kidney Failure, Acute Renal Failure
Left Dorsal Displacement of Large Colon with Nephro-Splenic Entrapment
Kidney Failure, Chronic Renal Failure
Viral Upper Respiratory Tract Infections, Generally
Large Colon Mechanical Obstruction, Generally
Bastard Strangles
Equine Anaplasmosis
Abdominal or Internal Abscess, Generally
Pneumonia, Pleuropneumonia & Pleuritis, Generally
Choke, Esophageal Feed or Foreign Body Obstruction
Viral Infection, Non-Specific
Intestinal Lymphosarcoma
Recurrent Airway Obstruction, RAO
Potomac Horse Fever, Neorickettsiosis
Aflatoxicosis, Aflatoxins
Acute Respiratory Distress Syndrome, ARDS
Bastard Strangles
Clostridial, Clostridium Colitis (in Adult)
Red Maple Leaf Toxicosis
Stress or Anxiety, Generally
Equine Proliferative Enteropathy, EPE
Cholangiohepatitis, Cholelithiasis
Right Dorsal Displacement of Large Colon
Cheek Tooth or Molar, Fractured or Broken
Adhesions, Intra-Abdominal
Stomach Impaction
Vaccination Reaction
Fracture of Incisive Bone of Upper Jaw or Mandibular Incisors Lower Jaw
Ascarid Worm Impaction
Neoplasia, Tumor or Cancer, Thorax
Theiler's Disease, Serum Hepatitis or Sickness
Poisonous Snake Bite, Rattlesnake or Pit Viper
Ileal Impaction
Blister Beetle Toxicity
Aging Changes, Generally
Carbohydrate or Grain Overload
Hepatic Encephalopathy
Abscess Near Anus, Vulva or Tail Base
Conditions Affecting Red Blood Cells, Generally
Monensin Toxicity
Leukemia, Cancer, Blood or Bone Marrow
Neoplasia, Tumor or Cancer, Kidney
Clostridial Muscle & Fascia Infection (Myonecrosis)
West Nile Virus, WNV
Black Locust Tree Toxicity
Onion Toxicity
Eastern, Western & Venezuelan Equine Encephalomyelitis
Infarcted Intestine or Colon
Liver Abscess
Equine Viral Arteritis, EVA
Burn, Chemical, Toxin, Caustic Substances Ingested & Irritating Mouth, Lips, Tongue
Vesicular Stomatitis, VS
Equine Herpesvirus 1 & 4, Rhinopneumonitis
Coronavirus Entero-Colitis
Poisoning by Cardiotoxic Plants, Generally
Borna Disease
Blue Green Algae Toxicity
Bacteremia, Septicemia (in Adult)
Equine Piroplasmosis, EP
Uterine Torsion
Adrenal Insufficiency
Equine Infectious Anemia, EIA
Nitrate Toxicity From Plants or Fertilizer
Fracture of Mandible or Lower Jaw
Congestive Heart Failure, CHF
Intestinal Foreign Body
Rectal Tear
Locoweed Toxicity
Neoplasia, Tumor or Cancer, Sinus or Nasal Passage
Neoplasia, Tumor or Cancer, Liver
Smoke Inhalation, Pneumonitis
Liver Disease, Acute Hepatitis
Pyrrolizidine Alkaloid Plant Toxicity
Protein-Losing Intestinal Diseases, Generally
Stomach Outflow Obstruction
Small Strongyle Infestation
Internal Ear Infections
Temporohyoid Osteoarthropathy
Sleep Deprivation
Kidney & Ureteral Stones
Plants Causing Salivation & Mouth Irritation
White Snakeroot Toxicity
African Horse Sickness, AHS
Equine Herpes Myeloencephalitis, EHM
Mare Reproductive Loss Syndrome, MRLS
Guttural Pouch Mycosis
Japanese Encephalitis
Cecal Disorders, Generally
Fractured or Broken Ribs (in Adult)
Phenothiazine Toxicity
Arsenic Toxicity
Ruptured Aorta, Ruptured Aortic Aneurysm
Larkspur, Monkshood Toxicity
Plant or Weed Toxicity, Generally
Poison Hemlock or Water Hemlock Toxicity
Multiple Myeloma
Hypoglycemia, Low Blood Sugar
Screwworm Myiasis
Black Walnut Shavings Toxicity
Conjunctivitis, Generally
Blue Weed, Patterson's Curse Toxicity
Equine Grass Sickness
Multisystemic Eosinophilic Epitheliotrophic Disease, MEED
Diabetes Mellitus

POSSIBLE TREATMENTS or TherapiesTo Lessen or Resolve the Sign

Author: Doug Thal DVM Dipl. ABVP


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