投喂频率对大菱鲆幼鱼生长特性、组织结构和生理健康的影响OA

This study systematically investigated the effects of feeding frequency on growth performance,digestive enzyme activities,serum biochemical parameters,antioxidant capacity,hepatic and intestinal histological structure,and transcriptomic profiles of juvenile turbot(Scophthalmus maximus).An 8-week feeding trial was conducted with a fixed ration level of 2.8%of body weight,where fish were randomly assigned to four groups fed at different frequencies:1 meal per day(F1),2 meals per day(F2),3 meals per day(F3),and 4 meals per day(F4).The results indicated that weight gain rate(WGR)and specific growth rate(SGR)exhibited a trend of initial increase followed by subsequent decrease with the elevation of feeding frequency,with F2 and F3 groups showing significantly higher WGR and SGR than the F1 group(P<0.05).Feed efficiency(FE)in the F1 group was markedly lower than that in all other treatment groups(P<0.05).For digestive enzymes,pepsin and lipase activities first increased and then decreased as feeding frequency rose,whereas no significant differences in trypsin and amylase activities were detected across all groups(P>0.05).The serum levels of glucose(GLU),total cholesterol(T-CHO)and triglycerides(TG)in the F1 group were significantly lower than those in the other groups(P<0.05).With increasing feeding frequency,the total antioxidant capacity(T-AOC)and activities of superoxide dismutase(SOD),catalase(CAT)and glutathione peroxidase(GSH-Px)presented a gradual declining trend.Specifically,T-AOC and SOD activities in F1 and F2 groups were significantly higher than those in F3 and F4 groups(P<0.05),while malondialdehyde(MDA)content showed an opposite variation tendency to the aforementioned antioxidant indices.Histological examination further revealed that the height of intestinal villi and microvilli increased with the rise of feeding frequency,and the F4 group possessed significantly higher villi than all other groups(P<0.05),whereas more severe hepatic vacuolization was observed in the liver of F4 group.Transcriptomic analysis demonstrated that feeding frequency significantly modulated the circadian rhythm pathway and arginine biosynthesis pathway.The expression levels of clocka and clockb in the F1 group were significantly down-regulated compared with those in F3 and F4 groups,while per1b and arg1 exhibited an opposite expression pattern.In conclusion,the optimal feeding frequency for juvenile turbot under the present experimental condition is 2 meals per day,which can achieve satisfactory growth performance and high feed utilization efficiency.Excessively high feeding frequency exerts negative impacts on antioxidant status and hepatic health,and the circadian rhythm and arginine biosynthesis pathways play crucial regulatory roles in mediating the physiological responses of juvenile turbot to feeding frequency.