Dietary nucleotides: a novel supplement in fish feeds 2. Effects on vaccination, salt water transfer, growth rates and physiology of Atlantic salmon (Salmo salar L.)

Trials were carried out in Atlantic salmon to determine the effects on vacc ine efficacy, vaccination and salt water transfer stress, growth performanc e and intestinal morphology of the inclusion in salmon diets of supplementa l nucleotides. When added to normal salmon feeds at a combined inclusion le vel of 0.03%, these additional nucleotides were shown to significantly enha nce the efficacy of vaccination as indicated by elevated antibody titres (1 /144 with nucleotide diet vs, 1/60 with control diet) and lower (although n on-significant) mortality following challenge, Significantly reduced blood chloride levels following salt water transfer was indicative of a greatly e nhanced capacity for osmoregulation. Increases were also observed in red bl ood cell levels, Furthermore, the checks in growth rates normally following these particular physical stressors were negated, with fish fed nucleotide -supplemented diets having a 15-22% weight advantage after 8 weeks (5 weeks following each of the two stress events). The growth benefits described fo llowing feeding with nucleotide-supplemented diets, even after just 3 weeks , could be due in part to an increase in the mucosal surface area of the gu t due to significantly enhanced intestinal fold morphology. (C) 2001 Elsevi er Science B,V. All rights reserved.