Optimal amounts of coconut oil in diets improve the growth, antioxidant capacity and lipid metabolism of large yellow croaker (Larimichthys crocea)

The purpose of this study was to investigate the effect of different dietary coconut oil (CO) levels on growth, antioxidant capacity and lipid metabolism of juvenile large yellow croaker (Larimichthys crocea). Five iso-nitrogen (45% crude protein) and iso-lipid (13% crude lipid) experimental diets were prepared by replacing 0% (the control), 25%, 50%, 75% and 100% fish oil with coconut oil. The results showed that dietary CO had no significant effect on survival rate (SR, P > 0.05). However, the specific growth rate was increased significantly when compared with the control group when fish were fed the diet with 50% CO (P < 0.05). The saturated fatty acids were increased significantly with increasing dietary CO in the liver and muscle, whereas the content of n-3 PUFA was decreased significantly (P < 0.05). The highest activities of glutathione peroxidase and superoxide dismutase in the liver were recorded in fish-fed diet with 50% CO; conversely, the content of malondialdehyde was significantly decreased (P < 0.05). The mRNA expression of peroxisome proliferator-activated receptor α, carnitine palmitoyl transferase 1 and acyl-CoA oxidase reached the highest levels in fish-fed diet with 50% CO. To some extent, this indicated that the rapid oxidation reaction of fatty acids to provide energy may be the reason for the rapid growth of large yellow croaker. In conclusion, fish-fed diet with 50% CO increased the growth rate and antioxidant capacity. Therefore, the optimal replacement level of CO to FO in the diet should be 50%.