| Experiment one:Effects of cyclic starving-feeding strategy on the growth,body composition and serum biochemical parameters of Korean rockfishThe effects of cyclic starvation and refeeding on the growth,body composition,serum parameters and muscle fatty acids of Korean rockfish.The experiment was divided into five groups: control(daily feeding),7F-1R(feeding for 7 days,starvation for 1 day),5F-1R(feeding for 5 days,starvation for 1 day),3F-1R(feeding for 3 days,starvation for 1 day),and 6F-2R(feeding for 6 days,starvation for 2 days),three in each group in parallel.Commercial feed was fed during the experiment and lasted for 72 days.The results were as follows: 1)The weight gain rate and final body weight of the experimental group were significantly lower than those of the control group.There was no difference in feed conversion ration among the groups.The specific growth rate during the Korean rockfish feeding period increased with the decrease of feeding days,and the experimental groups were significantly higher than the control group.There were no significant differences in the viscerosomtic index and intestine-somatic index among the groups,and the hepatosomatic index of 3F-1R was significantly lower than that of the control group.The condition factor of control and 7F-1R was not significantly different from that of the remaining groups.The daily feed intake of Korean rockfish increased as the number of feeding days decreased.2)There was no significant difference in crude protein,water content and ash content of Korean rockfish under different feeding methods.The crude lipid content of 7F-1R group was the lowest,which was significantly lower than that of control group and 3F-1R group.There was no significant difference in crude lipid content between the other experimental groups and the control group.There was no significant difference in crude fat,water content and ash content of Korean rockfish.There was no significant difference in crude protein content between the experimental groups and the control group except 3F-1R.3)The total cholesterol content of 7F-1R was the lowest,and there was no significant difference between control group and other experimental groups.6F-2R high density lipoprotein cholesterol was significantly higher than that in the control group,and there were no significant differences between the other groups.The low-density lipoprotein cholesterol was significantly higher in each experimental group than in the control group.There was no significant difference in free fatty acids between 7F-1R and the control group,but it was significantly higher than that in the other experimental groups.The content of triglyceride in each experimental group was not significantly different from that in the control group.There was no significant difference in total protein content among the groups.The albumin content of 3F-1R was not significantly different from that of the control group,and was significantly lower than that of the other experimental groups.The glucose content of each experimental group was significantly lower than that of the control group,and the glucose content of 5F-1R and 6F-2R was the lowest.Under different feeding methods,the sod activity of 5F-1R was the highest,which was significantly higher than that of 6F-2R,and was not significantly different from other groups.The aspartate aminotransferase activity of 3F-1R and the control group was significantly higher than that of the other experimental groups,and there was no significant difference between the other experimental groups.The control group and 7F-1R Alt activity were significantly lower than the other experimental groups,and 5F-1R Alt activity was the highest.4)The contents of SFA(saturated fatty acid),MUFA(monounsaturated fatty acid)and PUFA(polyunsaturated fatty acid)in muscle were not significantly different from those in the control group.In conclusion,under the present experimental conditions,only part of the compensatory growth of Korean rockfish could be reflected,and the compensatory growth of Korean rockfish was achieved by increasing the daily feed intake rather than by increasing the feed conversion rate.To obtain maximum growth rates,it is recommended to feed as much as possible when available.Experiment two:Molecular regulatory mechanism and potential biomarker screening of Korean rockfish response to starvation stressThe purpose of the study was to clarify the detailed molecular mechanisms underlying starvation stress in Korean rockfish(Sebastes schlegelii)through liver transcriptome and metabolome analysis.The control group(CG)was fed daily,and the experimental group(EG)was fasted for a period of 72 days.After the cultivation experiment,the liver of Korean rockfish was divided into two equal parts,one for transcriptome analysis and the other for metabolome analysis.The experimental results are as follows: 1)No mortality of Korean rockfish was observed during the experiment.The control group showed an increase in body weight(mean 38.21 g),while the experimental group showed a decrease in body weight(mean 3.79 g),mainly due to a significant reduction in the body components of fat and protein.2)1359 differentially expressed genes were screened by transcriptome analysis,including 551 upregulated genes and 808 downregulated genes.Among the top 20 enriched pathways in GO analysis,12 were enriched in biological processes,3 in molecular functions,and 5 in cellular components.The pathways enriched in KEGG analysis involved cell growth(cell cycle,P53 signaling pathway),lipid metabolism(PPAR signaling pathway,fatty acid metabolism,steroid biosynthesis,fatty acid biosynthesis and degradation,adipocytokine signaling pathway),and signal transduction(AMPK signaling pathway),among which the regulation of the cell cycle and fatty acid metabolism played a core role in the response of Korean rockfish to starvation stress.Korean rockfish downregulated cell cycle-related genes to respond to starvation stress.3)Metabolome analysis screened out 569 differentially expressed metabolites,including 208 increased and 361 decreased.There were 12 significantly enriched KEGG pathways,including purine metabolism,riboflavin metabolism,histidine metabolism,oxidative phosphorylation,taurine and hypotaurine metabolism,sphingolipid metabolism,ABC transporters,biotin metabolism,ascorbate and aldarate metabolism,glycolysis/gluconeogenesis,thiamine metabolism,and vascular smooth muscle contraction.The most representative pathway was purine metabolism.4)Starvation stress inhibited the synthesis of fat and fatty acids,and promoted the metabolism of fatty acid breakdown for Korean rockfish.After experiencing starvation stress,Korean rockfish had five different fatty acids(C22:6 n-3;C22:5 n-3;C20:5 n-3;C20:4 n-3;C18:3 n-6),which can be potential biomarkers for starvation stress.These experimental results provide new clues for understanding the role of fatty acid metabolism and the cell cycle in fish under starvation stress,and provide references for promoting the identification of biomarkers for starvation stress and the research on stress-resistant breeding. |
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