Feeding Strategy Study For Pearl Gentian Grouper In Recirculating Aquaculture Systems

Correct feeding management is the key to the industrial recirculating aquaculture.Appropriate feeding strategy can prevent over-feeding,reduce feed waste and environmental pollution,save production cost,promote the growth of cultured fish and improve production efficiency.The most important factors in feeding strategy are feeding frequency and feeding rate.In order to explore the mechanism and the effect of feeding frequency and rate on the growth of the fish cultured in industrial recirculating aquaculture,1)the metabolic characteristics of pearl gentian grouper(Epinephelus lanceolatus ♂ × Epinephelus fuscoguttatus ♀)with initial body weight of(469 ± 75)g cultured at different feeding frequency were studied based on TM wide target metabolomics method.A total of 180 experimental fish were fed in 3 sets of recirculating aquaculture systems each with 3 tanks for 60 days.They were divided into three groups: Low feeding frequency group(LF,once a day,8:00),Medium feeding frequency group(MF,twice a day,8:00,17:00)and High feeding frequency group(HF,4 times a day,8:00,11:00,14:00,17:00).The body weight of each fish was measured on the 0th day,17 th day,30 th day,45 th day and 60 th day.Three liver samplesof group LF and HF gained on the 60 th day were selected for TM wide target metabonomic analysis;2)The growth performance of pearl Gentian Grouper(117.3 ± 9.1)g was studied with different feeding rates.The fish under the experiment were divided into 3 growth stages and farmed for 8 weeks.Three feeding rates were set up with3 feeding rate groups: Low feeding rate group(LR),Medium feeding rate group(MR)and High feeding rate group(HR).A total of 360 fish were reared in 3 recirculating aquaculture systems with 3 tanks each for 3 weeks.The body mass of each fish was measured at the beginning and at the end of each week.The results showed that 1)the specific growth rate(SGR)of group HF was significantly higher than that of group MF and group LF(P < 0.05),and a total of 157 discrimination metabolites were detected,of which 121 were up-regulated and 36 down-regulated in group HF compared with group LF,including L-thyroxine up-regulated and guanidine acetic acid down-regulated,and the abundance of the former and the latter were positively and negatively correlated with the specific growth rate.KEGG pathway enrichment analysis showed that amino acid biosynthesis,tricarboxylic acid cycle,glucose metabolism,fat metabolism,amino acid metabolism,glutathione metabolism and c AMP signal pathway were affected by feeding frequency.Moreover,the results showed that increasing feeding frequency was capable of increasing specific growth rate,and feeding frequency affected growth metabolism;2)The growth of pearl gentian grouper increased with the increase of feeding rate and then became stable;The specific growth rate,mass gain rate and daily mass gain rate of medium feeding rate group(MR)were higher than those of low feeding rate group(P < 0.05),and there was no significant difference compared with the high feeding rate group(P > 0.05),and the differences between groups decreased with the extension of breeding time.There was no significant difference in feed conversion rate among all groups.The feed conversion rate can be as low as0.7～0.8 under the optimum feeding rate.The optimal feeding rates were 1.88～1.94%,1.75～1.88% and 1.31～1.49% at different growth stages of 115.0～170.4 g,170.4～209.8 g and263.9～325.5 g.Thus,it was concluded that this study can provide data basis and theoretical basis for efficient aquaculture of the factory recirculating aquaculture of pearl gentian grouper.