Effects of dietary natural mineral materials to identify the antibiotic replacer in Rainbow trout, Oncorhynchus mykiss

Abstract

Two experiments were conducted to evaluate the effects of dietary natural mineral materials to identify the antibiotic replacer in rainbow trout, Oncorhynchus mykiss. In the first experiment, rainbow trout averaging 2.7 ± 0.02g (mean±SD) were fed one of the Six experimental diets; a basal commercial diet without natural mineral was used as a control (Con), one oxytetracycline (OTC) supplied diet and other Four diets were added to different natural mineral like Yellow loess (YL), Macsumsuk (MS), Songgang stone (SG), Barley stone (BS) at 0.4% of each diet. At the end of the feeding trial, weight gain (WG), specific growth rate (SGR), feed efficiency (FE) and protein efficiency ratio (PER) of fish fed YL diet were higher than those of fish fed CON diet. Non-specific immune responses in Superoxide dismutase, Myeloperoxidase, Nitroblue tetrazolium and lysozyme activity of fish fed YL diet were higher than those of fish fed CON diet. However there were no significant differences among fish fed SG, YL and OTC diets. During the Aeromonas salmonicida challenge test, cumulative survival rate of fish fed SG, YL, MS and OTC diets were significantly higher than those of fish fed CON diet. However, there were no significant differences in cumulative survival rate among fish fed CON and BS diets. In the second experiment, rainbow trout averaging 261.5 ± 3.5g (mean±SD) were fed one of the four experimental diets; a basal commercial diet without natural mineral was used as a CON, one OTC supplied diet and other two diets were added to different natural mineral like YL, SG at 0.4% of each diet. At the end of the feeding trial, growth performance (WG, FE, SGR and PER) of fish fed SG and YL diets were significantly higher than those of fish fed CON diet. However there were no significant differences in growth performance among fish fed SG, YL and OTC diets. Non-specific immune responses (SOD, MPO and lysozyme activity) of fish fed SG and YL diets were significantly higher than those of fish fed CON diet. The results indicated that, dietary yellow loess and songgang stone at 0.4% could be an alternative of oxytetracycline replacer in juvenile and sub-adult rainbow trout.