Exposure to Feedborne Mycotoxins T‐2 Toxin or Ochratoxin A Causes Increased Mortality of Channel Catfish Challenged with Edwardsiella ictaluri

Abstract

AbstractTo evaluate the effect of mycotoxins on the disease resistance of juvenile channel catfish Ictalurus punctatus, we conducted an experiment in aquaria under controlled environmental conditions. Catfish were fed a nutritionally complete semipurified diet containing two concentrations of either T‐2 toxin (1.0 or 2.0 mg/kg diet) or ochratoxin A (OA; 2.0 or 4.0 mg/kg diet). Mycotoxins were supplied as pure, crystalline T‐2 toxin diluted to a known concentration in a carrier of casein and Aspergillus ochraceus culture material containing a known concentration of OA. After 6 weeks of feeding, catfish were challenged by immersion in situ with a virulent isolate of Edwardsiella ictaluri suspended in nutrient broth that provided an estimated 2.25 × 106 colony forming units per milliliter of water. At 21 d postchallenge, significantly (P < 0.05) greater mortalities occurred among catfish fed T‐2 toxin, 1.0 or 2.0 mg/kg diet (84.11% and 99.30%, respectively) than among control fish. Fish fed the OA diet (4.0 mg/kg) also had significantly higher mortality (80.49%) than control‐fed catfish, which experienced 68.28% mortality. Results indicate that juvenile channel catfish fed feedborne mycotoxins T‐2 toxin or OA had significantly greater mortality when challenged with E. ictaluri.