Diabetogenous symptoms in pellet fed hatchery-reared Atlantic salmon smolts (Salmo salar).

• Main Author: Drouin, Maurice Albert.
• Format: Thesis
• Language: unknown
• Published: Université d'Ottawa / University of Ottawa 1978
• Subjects: Agriculture, Fisheries and Aquaculture.; The Islets; Atlantic salmon; Salmo salar
• Online Access: https://dx.doi.org/10.20381/ruor-8467; http://www.ruor.uottawa.ca/handle/10393/10814

The profitable rearing of the Atlantic salmon (Salmo salar L.) requires artificial diets high in carbohydrates or fats or both in order to avoid the high cost of protein feed; this practice is monitored by growth criteria such as animal length and body weight. The present study investigates the physiological state of hatchery-reared salmon smolts raised under cage culture conditions and fed a commercial pellet food of elevated carbohydrate content. Our results show metabolic disturbances that strongly suggest a diabetogenous situation: hyperglycemia, hypertriacylglycerolemia, some glucosuria and occasional ketonuria. Histopathological examination confirms the initial suggestion: significant reduction of the beta to alpha cell ratio in the islets of Langerhans, frequent alteration of the disposition of insular cells, hydropic changes in the B cells such as degranulation, vacuolization and nucleic pyknosis, evidence of hypertrophy and hyperplasia of B cells and pronounced neoformation of islet tissue. In addition, hyalinization of both the exocrine and the endocrine pancreas was observed as well as fibrosis, lipomatosis and microangiopathy of the exocrine acinar tissue and an increase in intrapancreatic nerve cell number. In conclusion, the smolts fed the pellet diet displayed a syndrome reminiscent of mammalian diabetes; a comparison is drawn between diabetes mellitus and the observed form of salmon diabetes. The study emphasizes the need to involve physiological criteria in the assessment of the suitability of artificial diets especially in the rearing of healthy salmon intended for restocking of natural environments.