投喂水平和投喂频率对大规格花鲈生长、消化及非特异性免疫能力的影响OACHSSCD

[Objective]This study aimes to investigate the effects of feeding level and frequency on the growth performance,feed utilization,digestive enzyme activities,non-specific immunity and anti-stress ability of large sized Japanese seabass(Lateolabrax japonicus),thereby providing a scientific basis for developing feeding strategies for cage culture of large-sized Japanese seabass.[Method]The experiment was conducted in a sea cage culture system using spotted seabass with an initial body mass of(250.32±7.58)g as the research subject.For the feeding level trial,a feeding frequency of 2 times/d was adopted,with four feeding levels at 1%,2%,3%,and 4%of body mass.For the feeding frequency trial,apparent satiation feeding was implemented,with three feeding frequencies at 1,2,and 3 times/d.Each treatment had three replicates,and each replicate contained 20 fish.After a 70-day culture,parameters including growth performance,body composition,digestive enzyme activity,serum non-specific immunity,and stress resistance indices were measured.[Result]1)Results of the feeding level trial showed that,the mass gain rate and specific growth rate of Japanese seabass reached their maximum values in the 4%feeding level group(106.18%and 1.03%/d),which were significantly higher than those in the 1%group(80.42%and 0.84%/d),but showed no significant differences compared with the 2%and 3%groups.The feed conversion ratio was lowest in the 2%group(1.23),significantly lower than that in the 3%and 4%groups(1.44 and 1.58).The hepatosomatic index and viscerosomatic index were also highest in the 4%group.The whole-body crude lipid mass fraction was highest in the 4%group(30.97%),significantly higher than that in other three groups,while the crude protein content showed an opposite trend.No significant differences in muscle crude protein or crude lipid contents were observed among the groups.The activities of intestinal protease and lipase were relatively high at the 2%and 3%groups.The superoxide dismutase of serum activity was highest in the 3%group(284.97 U/mg),significantly higher than that in the 1%and 4%groups but not significantly different from the 2%group.Conversely,the malondialdehyde molality reached its maximum in the 1%group(11.32 nmol/mg).The activities of alanine aminotransferase and aspartate transaminase exhibited trends opposite to that of superoxide dismutase.In the 2%and 3%groups,the creatine kinase,corticosterone and adrenocorticotropic hormone contents of serum were relatively low,significantly lower than those in the 1%and 4%groups.2)Results of the feeding frequency trial showed that,the mass gain rate and specific growth rate of Japanese seabass peaked in the 2 times/d group(80.42%and 0.84%/d),which were significantly higher than those in the 1 time/d group(69.80%and 0.76%/d),and the feed conversion ratio showed an opposite trend to mass gain rate.The condition factor showed no significant difference between the 2 and 3 times/d groups,and both values were significantly higher than that in the 1 time/d group.Different feeding frequencies had no significant effect on the chemical composition of whole body or muscle.Intestinal protease activity was highest at the 2 times/d group(715.63 U/mg),and lipase activity reached relatively high levels in the 2 and 3 times/d groups(1.40 and 1.58 U/g),both significantly higher than that in the 1 time/d group.The superoxide dismutase activity of serum was highest in the 2 times/d group,significantly higher than that in the other two groups,and the activities of lysozyme and alkaline phosphatase showed the same trend as superoxide dismutase.The creatine kinase,corticosterone and adrenocorticotropic hormone contents of serum were relatively low in the 2 and 3 times/d groups,significantly lower than those in the 1 time/d group.α=0.05[Conclusion]Under the conditions of this study,considering practical production and cost reduction,a feeding level of 2%of body mass and a feeding frequency of 2 times/d are recommended for large-sized Japanese seabass.