GROWTH-PERFORMANCE AND RESPIRATORY BURST ACTIVITY IN RAINBOW-TROUT TREATED WITH GROWTH-HORMONE AND VACCINE

Size-selected (167+/-11 mm) female rainbow trout were: given a high (1 .8 mu g g(-1) body weight per week) or low (0.35 mu g g(-1)) dose of r ecombinant bovine growth hormone (GH), delivered by cholesterol pellet implant; injected with a commercial bivalent (vibriosis-furunculosis) vaccine; provided with each dose of GH plus vaccine; implanted with a pellet alone; or left untreated (N=20 per group). Growth in each trea tment group was monitored over a 7 week period. Four weeks into the tr ial, and at trial termination, head kidney neutrophils were quantified using a histochemical method, and their respiratory burst (CL) respon se evaluated (N=10 per group). By week 4 of the trial, high dose GH tr eatment was observed to enhance the CL response of vaccinated fish (P< 0.05) above that of control and other groups. High dose GH treated ani mals also returned greater, although relative to week 4 data significa ntly lower, CL response at trial termination. Vaccination had an overa ll negative effect (P<0.05) upon trout growth performance during the t rial, although this consequence was annulled when vaccine was co-admin istered with high dose GH. When considered conjointly with the finding s of others, the results of the present investigation provide evidence in support of the existence of a hypothalamo-pituitary-immune axis in teleosts. (C) 1997 Academic Press Limited.