Effects of dietary chromium yeast and astaxanthin on the growth performance, anti-oxidative capacity, and resistance to heat stress of abalone Haliotis discus hannai

This study was aimed at evaluating whether dietary chromium yeast (CrYst) and astaxanthin (ASTA) could enhance the growth performance, anti-oxidative capacity, and resistance to heat stress of abalone Haliotis discus hannai (initial body weight: 1.14 +/- 0.10 g; initial shell length: 19.20 +/- 0.87 mm) after a 120-day feeding trial. Based on the basal diet, the other three experimental diets were designed with supplementation of 2 mg/kg of CrYst, 80 mg/kg of ASTA, and 2 mg/kg of CrYst + 80 mg/kg of ASTA, respectively. The results showed that supplementation of 2 mg/kg of dietary CrYst significantly increased weight gain rate and the daily increment in shell length of abalone (P < 0.05). However, 80 mg/kg of dietary astaxanthin supplementation had no significant effects on the growth (P > 0.05). Meanwhile, there were no significant differences in feed intake and feed conversion ratio among all the groups (P > 0.05). Meanwhile, adding 2 mg/kg of CrYst and/or 80 mg/kg of ASTA into the diet improved the anti-oxidative capacity in serum and hepatopancreas, increased the gene expression of hsp70 and hsp90 in the hepatopancreas, and reduced the cumulative mortality and falling rate of abalone during the heat stress. In conclusion, dietary supplementation of CrYst and/or ASTA had positive effects on growth and anti-stress of abalone.