Nutritional steatitis (yellow fat disease) in cultured silver catfish Rhamdia quelen associated with rancid feed.

Nutritional steatitis (yellow fat disease) caused by vitamin E (vitE) deficiency is typically associated with diets high in unsaturated fatty acids or/and low levels of vitE. This work describes, for the first time, an outbreak of nutritional steatitis in cultured silver catfish Rhamdia quelen in Argentina. Necropsy, histopathology, bacteriology and molecular studies of the affected fish were performed. In addition, peroxide level and vitE concentration of the fish feed were measured. Affected specimens had firm, yellowish-brown dermo-hypodermal nodules located in the adipose fin and dorsal region of the body. Histologically, lesions consisted of fat necrosis and multifocal granulomatous lobular steatitis, primarily affecting the subcutaneous and intermuscular adipose tissue, and occasionally, the coelomic fat. Feed analyses revealed a high peroxide value (41.2 mEq kg-1), indicative of rancid feed, and a low concentration of vitE (2.7 IU kg-1). In this case, fish had been fed rancid food with an inadequate value of vitE, leading to the development of nutritional steatitis caused by vitE deficiency.