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Objectives: A Dexter cow aged five years in the fifth month of pregnancy was referred to the Clinic for Ruminants and Swine, Department of Veterinary Medicine, Freie Universität Berlin, Germany, by a local practitioner due to general weakness and ataxia that did not respond to treatment.
Materials and Methods: At admission, the cow was clinically examined according to Rosenberger  and blood samples were obtained for laboratory testing. An intravenous glucose tolerance test was performed. While plasma glucose concentrations were determined in the laboratory of the clinic, serum samples for determination of insulin were sent to the Endocrinology Laboratory, Clinic for Cattle, Tieraeztliche Hochschule Hannover. A radioimmunoassay was applied for the quantification of serum insulin concentrations in cattle1.
Results: The general condition and demeanor of the cow were severely impaired. The cow demonstrated an uncertain stance characterized by inability to properly support the body weight by its legs. When walking, the animal showed ataxic movements and a hypermetric gait. Besides the symptoms described above, the neurological examination demonstrated bilateral mydriasis as well as delayed pupillary reflexes (direct/indirect). Results of blood analysis revealed a persistent hypoglycemia (glucose levels: 1.4 – 1.9 mmol/l). The Dexter cow, however, did not respond with ketone body production or excessive lipomobilization in the face of hypoglycemia. Therefore, an insulin-secreting tumor was suspected and an intravenous glucose tolerance test (IVGTT) confirmed the latter assumption.
Conclusions: All treatment attempts including providing glucogenic nutrients and precursors (glycerol and propylene glycol) failed and the condition of the cow deteriorated during hospitalization. Due to the clinical condition and the unfavourable prognosis, euthanasia was elected and the animal was sent for necropsy to the Institute of Veterinary Pathology, Faculty of Veterinary Medicine (Freie Universität Berlin). At necropsy, multifocal, highly infiltrative, white-grey nodules were present in the pancreas. An immunohistochemical examination confirmed the clinical diagnosis of insulin-producing islet cell tumor in the pancreas.