In a goose flock consisting of 2300 birds of 6 months of age severe goitre was diagnosed. To the best of our knowledge this is the first report of naturally occurring goitre in geese, which is not related to the feeding of rapeseed meal. The major pathological findings included
retarded growth and plumage development, significantly (300%) increased relative thyroid weight, fat accumulation in the mesenteric and abdominal region, and lipid infiltration of liver and kidney cells. Subsequent hormone analysis showed undetectable thyroxine (T4 ) levels and a dramatic
drop in triiodothyronine (T3 ) plasma levels of the diseased geese. Thy- roidal histology displayed the typical signs of struma parenchymatosa. In order to get more information about the possible causes of the goitre, 10 geese from the af- fected farm were transferred into the laboratories
of the Central Veterinary Insti- tute. The geese were allotted into two groups. Group I received iodine supple- mentation for 55 days, while the other group served as sick control (Group S). Io- dine treatment caused a dramatic improvement in the birds™ clinical condition e x- cept in
plumage growth in Group I, while the clinical and main pathological signs of goitre remained unchanged or worsened in the untreated Group S. Contrary to this, the serum levels of thyroid hormones and responsiveness to thyrotropin re - leasing hormone (TRH) improved not only in Group I but
also in Group S. Almost euthyroid biochemical parameters were found after 55 days of iodine treatment in Group I and, surprisingly, a considerable improvement (especially in serum T3 levels) occurred also in Group S. These findings confirm the diagnosis of goitre but also call attention to
the fact that iodine deficiency was not the only factor eliciting the disorder. The underlying possible goitrogenic substance could not be traced down.