| Planting aquatic plants is an important way for the ecological cultivation of crayfish.Planting appropriate aquatic plants is the key to improving the production and quality of crayfish.At present,there are no systematic reports on the selection of species of aquatic plants in breeding ponds,the effects of different aquatic plants on the growth performance,nutritional composition and the optimal density of crayfish.In this study,In this study,the common aquatic plants in crayfish culture were used as point of penetration,explored the contribution of different aquatic plants to crayfish food source,growth performance,and nutritional composition,and comparison of feeding habits,growth performance and digestive enzyme activity and antioxidant enzyme activity of crayfish with different stocking densities.The results are as follows:1.1.Effects of different aquatic plants on food contribution,growth performance and color of Procambarus clarkiiIn this study,4 experimental groups(Alternanthera philoxeroides,Elodea nuttallii,Hydrilla vcarticillata and Vallisneria spiralis;Grouped as AP,EN,HV and VS respectively)and 1 control group(FD group)were fed and fed with commercial feeds to culture Procambarus clarkii,and the culture period was 50 d.The contribution rate of four kinds of aquatic plant to the food source of Procambarus clarkii,growth performance and the chroma values(L a b)of hepatopancreas,muscle and carapace were measured and analyzed,we explored the species of aquatic plants suitable for transplantation in the culture of P.clarkii.The results showed that:(1)According to the calculation of SIAR mixed model,the contribution of four kinds of aquatic plants to the food source of P.clarkii is in order: EN > HV > VS > AP;(2)Hepatopancreas index and survival rate among groups there was no significant difference(P > 0.05).The final weight,the final length,the weight gain rate,the specific growth rate of P.clarkii in the HV group and EN group were significantly higher than those in the other groups(P < 0.05),there was no significant difference in the above growth indexes among the AP group,VS group and the control group(P > 0.05).(3)redness value(a)of Hepatopancreas,muscle and carapace and yellowness value(b)of muscle and carapace were the highest in the HV group(P <0.05).In conclusion,The contribution of HV and EN to the food source of crayfish is greater than that of feed,and their growth performance and color have been enhanced to a certain extent;The contribution of VS to the food source of crayfish is less than that of feed,and there is no significant effect on its growth performance;VS has a certain improvement on the color of crayfish,but the improvement effect is not as good as HV and EN.AP is inferior to HV,EN and VS in improving the contribution of food source and color.therefore,during the culture of P.clarkii,the choice of EN and HV for planting can not only reduce the feeding of feed,but also significantly improve the growth performance and color of P.clarkii.2.Comparison of nutritional composition of crayfish fed on different aquatic plantsIn order to study the effect of 4 kinds of aquatic plants on the nutritional composition of crayfish,this experiment set up an experimental group((AP,EN,HV and VS))and a control group(simulation aquatic plant).Crayfish with an initial body weight of(4.50 ± 0.50)g were cultured for 50 days.After the experiment,the conventional nutritional components,fatty acid composition,amino acid composition and nutritional value in the muscle and hepatopancreas of crayfish were compared and analyzed.The results showed that: 1.In terms of muscle tissue,there was no significant difference in crude protein content among the aquatic plants groups(P> 0.05),but they were significantly higher than those in the control group(P <0.05).The group had the highest content of crude fat in the liver and pancreas tissues of each aquatic plant group,which was significantly higher than that of the control group(P <0.05),and the contents of water and crude ash were the highest in the control group;The highest saturated fatty acid(SFA)content,no significant difference in monounsaturated fatty acid(MUFA)content between the groups(P> 0.05),the highest content of polyunsaturated fatty acids(PUFA)in the water peanut group,the water peanut group and bitter grass group The highest content of high unsaturated fats(HUFA);in terms of fatty acid composition of liver and pancreas,there is no significant difference in SFA and PUFA content among the groups,the MUFA content in the control group is the highest,and the HUFA content in the water flower group is the highest.The MUFA and HUFA contents of the HV group are the lowest;3.In terms of the amino acid composition in muscle tissue,there is no significant difference in the content of essential amino acids(EAA)between the groups,and the non-essential amino acid(NEAA)content and total ammonia of the HV group The highest acid(TAA)content;in terms of the amino acid composition of liver and pancreas tissue,the content of EAA,NEAA,and TAA were the highest in the control group;4.According to the chemical score results of crayfish muscle,the first limiting amino acid was Met-Cys,the Elodea group had the highest essential amino acid index(EAAI).In summary,in the 4 kinds of aquatic plants environment,the conventional biochemical,fatty acid and amino acid composition of crayfish muscles of HV and EN has a certain enhancement compared to the FD group.Aquatic plants can significantly increase the lipid accumulation of crayfish hepatopancreas tissues,among which EN and HV help to enhance the fatty acid nutritional flavor of hepatopancreas tissues,but aquatic plants have a certain negative effect on the amino acid composition of hepatopancreas tissues;The amino acid score found that the crayfish muscles of the HV group and the EN group had better nutritional value than the feed group.Therefore,in the cultivation of crayfish,HV and EN were selected for cultivation,has a certain effect on improving the nutritional quality and flavor of crayfish muscle.3.Comparison of growth performance and food contribution of crayfish with different stocking densitiesIn order to explore the suitable stocking density of crayfish,five density gradients(10,15,20,25,30/m2)were set up in the experiment.In an environment where the coverage of Elodea is 60%,the initial body mass of the culture is(4.50 ± 0.50)g crayfish(Procambarus clarkii)45 days.The growth performance and food source contribution of crayfish with different stocking density were compared.The results showed that the survival rate of 10/m2 was the highest,the weight gain rate of 10 and 15/m2 was higher than that of other density groups,and the terminal body length and body mass of 10/m2 density group were the highest.In the same stocking density group,the contribution of Elodea to the large size crayfish was higher than that of the small size crayfish,and the contribution of 25/m2 density group feed was the largest.With the increase of stocking density of large size crayfish,the contribution of feed to crayfish tends to increase.In conclusion,with the increase of stocking density,the growth performance of crayfish decreased.When stocking density was higher than 15/m2,the growth rate of crayfish decreased significantly. |
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