合成虾青素对豹纹鳃棘鲈的生长性能及体色的影响OA

This study was designed to investigate the effects of dietary synthetic astaxanthin supplementation on the growth performance and body coloration of Plectropomus leopardus,a commercially valuable marine carnivorous fish species whose market value is closely associated with its bright and uniform body color.A total of 504 healthy P.leopardus individuals with normal body color and an initial body weight of(323.56±14.64)g were selected from the same batch and randomly assigned to 4 experimental groups,with 3 independent replicates per group(42 fish per replicate).The basal diet,formulated to meet the basic nutritional requirements of P.leopardus,was supplemented with synthetic astaxanthin at gradient dosages of 0 g·kg-1(T0 group,as the blank control),1 g·kg-1(T1 group),2 g·kg-1(T2 group),and 3 g·kg-1(T3 group),respectively.The feeding trial was conducted under standardized aquaculture conditions(stable water temperature,dissolved oxygen,and pH)for a continuous period of 90 d,during which the fish were fed to apparent satiation twice daily.The results indicated that with the gradual increase of dietary astaxanthin concentration,the growth performance of P.leopardus showed a trend of first increasing and then slightly decreasing,and all astaxanthin-supplemented experimental groups outperformed the control group(T0)in terms of key growth indicators.Specifically,T2 group exhibited the optimal growth performance:the average body mass(BM),weight gain rate(WGR),and specific growth rate(SGR)of fish in T2 were significantly higher than those in the control group(P<0.05),while no significant difference was observed between T1 and T3 groups in these growth parameters(P>0.05).Regarding body color characteristics,dietary synthetic astaxanthin supplementation exerted a significant regulatory effect on the body color of P.leopardus compared with the control group(P<0.05).Among all experimental groups,fish in T2 group displayed the most uniform and intense red body color.With the increase of astaxanthin dosage in the diet,the body color of experimental fish gradually reddened;the original dark spots distributed on the head,lateral body,and tail skin gradually turned into bright orange-yellow,and the base of the pelvic fins changed from light red to deep red.To quantitatively evaluate the body color changes,a professional colorimeter was used to determine the color parameters[L*(brightness),a*(redness),and b*(yellowness)]of P.leopardus in each group at three key time points(30 d,60 d,90 d)during the trial.The colorimetric data revealed that the color parameters of all experimental groups showed a gradual stabilization trend with the extension of the feeding period.At 60 d and 90 d of the trial,L*,a*,and b* values of fish in T2 group were not only higher than those in T1 and T3 groups but also significantly higher than those in the control group(P<0.05),indicating that the body color of T2 group fish was brighter,redder,and more yellowish,which was consistent with the visual observation results.In conclusion,dietary supplementation with appropriate levels of synthetic astaxanthin can effectively improve the growth performance(including BM,WGR,and SGR)of P.leopardus and significantly enhance its body coloration and internal pigment deposition,thereby further improving the commercial value of this farmed fish.Based on a comprehensive analysis of growth performance indicators,body color characteristics,and skin pigment content data,the optimal supplementation dosage of synthetic astaxanthin in the diet of P.leopardus is determined to be 2 g·kg-1,which can achieve the best balance between promoting growth and optimizing body coloration.