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Effects Of Different Stocking Density On Goldfish Growth,Physiological Parameters And Expression Of Appetite Regulatory Factors

Posted on:2021-04-27Degree:MasterType:Thesis
Country:ChinaCandidate:J X LiFull Text:PDF
GTID:2493306545457854Subject:Fishery development
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The intensive high stocking density model can improve economic benefit within limited stocking area and is favored by a large number of aquaculture farmers,but excessively high stocking density often have a negative impact on fish health.Stocking density is an important environmental factor in aquaculture.The effect of culture density on fish was different among species.Therefore,it is of great significance to study the effect of stocking density on different fish species.Goldfish(Carassius auratus),also known as golden crucian,belongs to the family Cyprinidae under the order Cypriniformes and is a derivative species of long-time domesticated crucian.It is a common spectacular fish.It also has the advantages of easy domestication,moderate individual size and convenient blood sampling and is an ideal object for the study of fish growth and feeding.Based on the goldfish as the research object,this paper studies effects in different stocking densities for goldfish growth,physiological parameters and expressions of appetite regulatory factors.1.Effects of different stocking densities on growth indicators of goldfishHealthy goldfish with an initial body weight of 13.23 ± 0.60 g were selected and were feeding in three stocking densities(low stocking density at 3.29 g / L,medium stocking density at 7.40 g / L,and high stocking density at 14.79 g / L).Three replicates were performed in each stocking density,and growth indicators were calculated after28 days of different stocking densities.The results showed that the feeding rate,weight gain rate,specific growth rate,and hepatosomatic index decreased significantly with the increase of stocking density.The growth indicators of the low stocking density group were the best,and there were significant differences in three stocking density groups(P < 0.05).The body weight and body length of goldfish in the low stocking density group increased fastest.The body weight,body length and conversion ratio of the goldfish in the low stocking density group were significantly higher than those in the medium and high stocking density groups(P < 0.05),and there was no significant difference between the medium and high stocking density groups(P > 0.05).There was no significant difference in the condition factor and survival rate of the goldfish in three stocking density groups(P > 0.05).From the growth indicators,goldfish in the low stocking density group have the best breeding effect.2.Effects of different stocking densities on physiological parameter indicators of goldfishAfter 28 days of farming,9 fishes were randomly selected for each stocking density,and goldfish blood physiological parameter indicators were detected,containing blood glucose,total protein,cholesterol,triglycerides,creatinine,aspartate aminotransferase,alanine aminotransferase and blood urea nitrogen.The results showed that the content of triglyceride and the activities of aspartate aminotransferase and alanine aminotransferase decreased with the increase of stocking density,and there were significant differences among stocking density groups(P < 0.05).There was no significant difference in the blood glucose,total protein,cholesterol,creatinine,and blood urea nitrogen contents among the three stocking density groups(P > 0.05).The results suggested that the energy demand of goldfish increased under high stocking density,and high stocking density caused damage to the goldfish liver.3.Effects of different stocking densities on the expression of goldfish appetite regulatory factorsUsing RT-PCR and RACE methods,two full-length c DNA sequences of B-form leptins were cloned from the goldfish liver,named leptin-BⅠ and leptin-BⅡ.Both types of goldfish B-form leptin open reading frames are 509 bp and encode the mature peptide with a length of 168 amino acids.The protein structures of goldfish leptin-BⅠ and leptinBⅡ have the typical four-helix bundle conformation,belong to the class I cytokine family and are appetite suppressants secreted by the peripheral regulatory system.Using Quantitative Real-time PCR technology,the expressions in three stocking densities of four leptin mRNAs in goldfish liver and of appetite neuropeptide mRNAs in goldfish brain,containing anorexia neuropeptides(CCK,CART,MCH,and POMC)and anorectic neuropeptides(NPY,Apelin,Ag RP and Orexin),were detected after 28 days farming.The results showed that the expressions of four leptins,anorexia neuropeptide NPY,anorectic neuropeptide CCK,CART,and MCH mRNAs in the high stocking density group were significantly higher than those in the low and medium stocking density groups(P < 0.05),and there was no significant difference between the low and medium stocking density groups(P > 0.05).The expression of Orexin m RNA in the medium and high stocking density groups was significantly higher than that in the low stocking density group(P < 0.05),and there was no significant difference between the medium and high stocking density groups(P > 0.05).There was no significant difference in the m RNA expression levels of Apelin,Ag RP and POMC among stocking density groups(P > 0.05).The above results showed that when the stocking density reached 14.79 g/L,the m RNA expression levels of appetite regulators NPY,Orexin,CCK,CART,MCH and four leptins in goldfish increased,which synergistically participate in the stress response and change of feeding behavior of goldfish under the pressure of breeding.Based on the above results,the goldfish low density stocking group(3.29 g/L)in this experiment had the best stocking effect and the stocking effect gradually decreased with the increase of the stocking density.Therefore,under the intensive high stocking density model of goldfish,the appropriate reduction of the stocking density is conducive to the growth of goldfish.
Keywords/Search Tags:stocking density, growth indicators, appetite regulator factors
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