Interactive effect between dietary valine and isoleucine on growth performance, blood parameters and resistance against low salinity stress of Japanese flounder Paralichthys olivaceus

Abstract

The interaction between dietary valine (Val) and isoleucine (Ile) on growth, blood parameters, and tolerance against low salinity stress of Japanese flounder Paralichthys olivaceus was studied in a 60-day feeding trial. Fish (initial body weight: 3.57 ± 0.05 g) were fed six experimental diets containing different proportions of Ile and Val, two levels of Ile 0% (LI) and 2% diet (HI), combine with three levels of Val 0% (LV), 0.83% (MV), and 2.27% diet (HV), respectively. The results revealed that significant interactive effect of Ile and Val was found on body weight gain and feed conversion ratio, also stimulative effect was found in high Ile groups. Meanwhile, interactive effect of these two amino acids was also observed on high-density lipoprotein (HDL), the maximum of Ile with maximum of Val group has the highest concentration of HDL, which was significantly higher than other groups (p < .05). Moreover, no interaction was found on whole body proximate composition, muscle Ile and Val concentration, and tolerance ability against low salinity stress (reflected by LT50). But high level of Ile combined with high level of Val diet altered tolerance ability against low salinity stress of Japanese flounder. It would be indicated that dietary Ile and Val interacted in the diet of Japanese flounder, and the flounders fed the diet supplemented with 2% Ile and 2.27% Val was superior to the other groups on growth and blood parameters, and tolerance against low salinity stress.