Effect of dietary inclusion of yacon, ginger and blueberry meals on the growth, body composition and serum chemistry of juvenile olive flounder (Paralichthys olivaceus) and challenge test against

Abstract

The effect of dietary inclusion of yacon (YC), ginger (GG) and blueberry (BB) meals on the growth, feed utilization, body composition and serum chemistry of juvenile olive flounder (Paralichthys olivaceus) and resistance to Streptococcus iniae compared to a commercial probiotic (LF) (Lactobacillus fermentum) was investigated. Six hundred fish were randomly distributed into 15 of 50-L flow-through tanks (40 fish per tank). Five experimental diets were prepared in triplicates. The control diet (CON) contained no additive. 0.5% LF was included into the CON diet instead of water based on the manufacture’s recommendation. One percent of YC, GG and BB were included into the CON diet at the expense of wheat flour, referred to as the YC, GG and BB diets, respectively. Fish were fed with one of the experimental diets for 8 weeks. At the end of 4-week and 8-week feeding trials, fish were artificially infected with S. iniae and the cumulative mortality of fish was monitored for 8 days. No significant difference in survival, weight gain and specific growth rate of fish was observed at the end of 8-week feeding trial. None of feed utilization, serum chemistry and the whole body of fish was affected by the experimental diets. The cumulative mortality was significantly higher in olive flounder fed the CON diet compared to that of fish fed the YC, GG, BB and LF diets, starting at 48 h and 96 h until the end of 8-day post observation after S. iniae infection after 4-week and 8-week feeding trials, respectively. These results indicate that yacon, ginger and blueberry was the effective immunostimulants against S. iniae rather than growth promoter.