The Study Of Biological Flocs As Open Food For Larvae Of Loach (Misgurnus Anguillicaudatus)

This paper preliminary studies the influence of biofloc as the initial feeding of loach larval,the cultivation of biofloc,the analysis of nutrient component and the way to keep biofloc.Mainly discussed(1)The cultivation of biofloc;(2)The analysis of nutrient component of biofloc;(3)The study on biofloc as the initial feeding of loach larval;(4)Effect of biofloc on the removal of ammonia nitrogen by encapsulation-dehydration1?The cultivation of bioflocThis study aimed to investigate the effects of adding different nitrogen sources(ammonium chloride and compound feed)on the cultivation of biofloc.The experimental period was 12 d.The results show that the biomass of biofloc cultivated by Ammonium Chloride is larger than that by compound feed on 1~5 days.At fifth days,the biomass of biofloc of the ammonium chloride group and the compound feed group reached 1.6 ml/L and 3.2 ml/L,respectively.From6 to 10 days,the biomass of biofloc in the ammonium chloride group was larger than that in the compound feed group.At tenth days,the biomass of biofloc in the ammonium chloride group and the compound feed group reached 6.5 ml/L and 6.1 ml/L,respectively.The biomass of biofloc in the compound feed group was larger than that in the ammonium chloride group from11 to 12 days.At the end of the experiment,the biomass of biofloc in the ammonium chloride group and the compound feed group reached 7.2 ml/L and 8.8 ml/L,respectively.In terms of biomass of biofloc,it is better to use artificial compound feed to cultivate biofloc.But considering the following factors: first,in the process of predation and breathing,fish will eat part of biofloc,and in arge-scale production,this phenomenon will be more obvious;second,The effect of environmental change on fish feeding will have an adverse effect on large-scale production;Third,there is a certain proportion of fish feces in the biofloc which is obtained by artificial feeding,thus there is a risk of spreading disease.2?The analysis of nutrient component of bioflocThe study is aimed to analyze the nutrient component of biofloc and evaluate the nutritional value of biofloc as the initial feeding.According to the analysis results,the content of crude protein in biofloc is 29.14% to 30.24%,the content of crude fat is 2.63% to 3.25%,coarse fiber is 6.71% to 7.51%,ash is 13.83% to 14.66%,and carbohydrates is 33.5~36.5%.So far,there are few studies on the protein and fat demand of loach larvae.But by comparing the juvenile and adult loach and other fish protein and fat requirements,We can speculate that the suitable protein and fat demand for the loach larva are 38~40% and 7~10%,respectively.The results show thatthe protein and fat content of bioflocs in compared to the loach larvae demand is slightly lower.Although the larvae can increase food intake to meet the demand for protein and fat,in order to meet the needs of amino acids and fatty acids in the process of development and growth,especially the essential amino acid and fatty acid requirements are met,only bioflocs as the initial feeding of loach larvae is not the best choice.Therefore,On the one hand,the cultivation method of biofloc should be improved so as to improve the proportion of phytoplankton in biofloc.On the other hand,some nutrients can be added to the biofloc to meet the needs of the loach fish for protein and fat.3?The study on biofloc as the initial feeding of loach larvalThis study aimed to investigate the effects of using different initial feeding on the growth and survival rate of loach larval.The experimental period was 21 d.At the end of the experiment,the average lengths of the rotifer group,biofloc compound feed group,egg yolk group,and biofloc group were 27.3 mm,26.8 mm,23.1 mm,and 20.3 mm,respectively.The average survival rates of each group were 55.39 %,52.21 %,42.16 % and 34.20 %,respectively.The rotifer is most suitable initial feeding for the loach larval.Biofloc-compound feed can be used as the initial feeding when the rotifer is lacking.4? Effect of biofloc preservation on the removal of ammonia nitrogen by encapsulation-dehydrationThe biofloc was preserved by encapsulation-dehydration to investigate the effects of different activation time and preservation time on the removal rate of ammonia nitrogen.The results show that the removal rate of ammonia nitrogen increases with the prolongation of the activation time.The removal rate of ammonia nitrogen remained stable after 15 days.The biofloc was stored at 4 ? for 1 week,2 weeks,and 4 weeks,and the effect of different storage time on ammonia nitrogen removal was determined.After 7 days of experiment,the removal rate of ammonia nitrogen was reached 69.10 %?39.00 %?26.00 %,respectively.