Possible meningitis or encephalitis? Something with the nervous system? Hepatic disease possibly. ...
Hepatic encephalopathy is associated with behavioral changes in horses, ruminants, and swine. The severity of hepatic encephalopathy often reflects the degree of hepatic failure but does not differentiate between acute or chronic liver failure. Signs of hepatic encephalopathy range from nonspecific depression and lethargy to head pressing, circling, aimless walking, dysphagia, ataxia, dysmetria, persistent yawning, increased friendliness, aggressiveness, vicious behavior, stupor, seizures, or coma. Pharyngeal or laryngeal collapse with loud, stertorous inspiratory noises and dyspnea occurs in some cases of hepatic failure, especially in ponies. The pathogenesis of hepatic encephalopathy is unknown, but proposed theories include ammonia as a neurotoxin, alterations in monoamine neurotransmission (serotonin, tryptophan) or catecholamine neurotransmitters, imbalance between aromatic and short branch chain amino acids resulting in increased inhibitory neurotransmitters (γ-aminobutyric acid, L-glutamate), neuroinhibition due to increased cerebral levels of endogenous benzodiazepine-like substances, increased permeability of the blood-brain barrier, and impaired CNS energy metabolism. Although the signs can be dramatic, hepatic encephalopathy is potentially reversible if the underlying hepatic disease is resolved
What kind of blood work did they do? Has she had a fever? Does she have ataxia? How is her balance? How close did the vet check her over?
It could also be something nutritional related
