The effect of vaccination and vaccine components upon short-term growth and feed conversion efficiency in rainbow trout

The impact of single intraperitoneal injections (0.2 mi) of a commercial vaccine, its components and a novel adjuvant upon growth and feed conversion efficiencies (FCE) of rainbow trout (n = 35/tank in duplicate) was evaluated over a 7 week period. The vaccine contained a metabolisable oil-emulsion. Post hoc multiple comparison (Scheffe's method) using a set of contrasts included (i) vaccination vs. control; (ii) Aeromonas salmonicida cells vs, no cells; (iii) adjuvant (metabolisable oil) vs. no adjuvant; (iv) interaction effect between A. salmonicida cells and adjuvant; (v) differences between adjuvants; and (vi) adjuvants vs. control. Vaccination resulted in significant (P < 0.05) growth depression when compared to untreated controls. Over the duration of the trial, weight loss in vaccinated fish was 8%. Furthermore, it was determined that the effect of the vaccine upon growth was caused by cells (P < 0.05) rather than adjuvant and/or interactions between the two. Also A. salmonicida cells caused a significantly (P < 0.05) higher splenic index. Vaccination caused intra-abdominal adhesions and injection site lesioning. (C) 1999 Elsevier Science B.V. All rights reserved.