Effect of dietary astaxanthin on the growth performance, lipid composition and post-mortem skin colouration of red porgy Pagrus pagrus

A 120-day feeding trial was conducted to assess the possible effect of including dietary astaxanthin (ASTX), for different lengths of time prior to harvest, on red porgy growth performance, lipid and fatty acid composition and post-mortem skin colour. Four treatment groups were established with fish of initial weight of approximately 220 g. Control group was fed on a control diet (with no astaxanthin included) for the entire experiment. ASTX60 group was fed for the first 60 days of the trial on the control diet and 60 days before harvest on a diet with 100 mg of unesterified astaxanthin per kg(-1) of diet (ASTX diet). ASTX90 group was fed for the first 30 days of the trial on control diet and 90 days before harvest on ASTX diet. ASTX120 group was fed on ASTX diet during the complete experiment. Results showed an enhancement of certain growth parameters due to ASTX diet and feeding period. In addition, a lipid-lowering effect on whole fish and liver was observed with increased feeding time with ASTX diet, as well as a significant variation of liver and head kidney fatty acid profiles. Concerning skin colouration, only ASTX90 and ASTX120 treatment groups presented adequate hue values throughout the 7 days post-mortem, similar to those reported for wild red porgy. However, skin chroma was close to wild specimens in ASTX120 treatment fish only and up to day three post-mortem. Skin lightness (L*) was not affected by astaxanthin inclusion. Feeding red porgy for a period of 90-120 days before harvest on ASTX diet seems to affect red porgy growth performance, lipid content and fatty acid profile. However, to achieve an adequate skin colouration, throughout a post-mortem period of 7 days, ASTX diet should be given 120 days before harvest.