Effects of three different microalgae on growth performances and immune responses in juvenile rainbow trout, Oncorhynchus mykiss

Abstract

A six weeks feeding trial was conducted to evaluate three different dried microalgae on growth performances and immune responses in juvenile rainbow trout, Oncorhynchus mykiss, diets. Twelve groups of fifteen rainbow trout averaging 12.2 ± 0.11 g (mean ± SD) were randomly distributed into four treatments in triplicates rearing by the semi-recirculation system. Fish were fed four experimental diets such as CONT (a basal diet), CHLO (0.5% Chlorella sp.), HAEM (0.5% Haematococcus sp.), or SCHIZO (0.5% Schizochytrium sp.). Weight gain (%) and specific growth rate of fish fed HAEM diet were significantly higher than those of fed the other diets (P < 0.05). Whole-body moisture and crude protein from fish fed CONT and SCHIZO diets were significantly higher than the other diets. Whole-body crude lipid from fish fed HAEM were significantly higher than those from fish fed all the other experimental diets, whole-body ash from fish fed SCHIZO were significantly lower than those from fish fed the other diets (P˂0.05). Glucose levels from fish fed CHLO and SCHIZO diets were significantly lower than those from fish fed CONT and HAEM diets. Lysozyme activity from fish fed HAEM diet was significantly higher than those from fish fed the other diets (P<0.05). Fish were challenged by Vibrio anguillarum bacteria for 27 days after the feeding trial and the cumulative survival rate (%) from fish fed microalgae (CHLO, HAEM, and SCHIZO) diets were significantly higher than those from fish fed CONT diet (P <0.05). Therefore, these results suggest that microalgae in the diet (CHLO, HAEM, and SCHIZO) could be used as immune enhancers, and dietary HAEM could act as the potential growth promoter in juvenile rainbow trout.