| The industrial farming of shrimp is a high-density,intensive farming model.A controlled farming environment.High yield and high risk are the main characteristics of factory farming.Over the past few years,shrimp factory farming in northern China has gained momentum but still faces many problems.Deterioration of the aquaculture environment caused by the frequent occurrence of diseases,the decline in the quality of shrimp owing to the degradation of germplasm resources,and environmental pollution resulting from the substandard discharge of aquaculture wastewater are threatening the sustainable development of the shrimp aquaculture industry.Therefore,the following studies are conducted in this paper to address the above problems of indoor factory farming.1.Effects of kelp residue with different particle sizes as carbon sources on biofloc culture and water quality control of L.vannamei in an indoor industrial aquaculture system.Biofloc technology(BFT)is an important way to realize the sustainable development of the aquaculture industry.The technology promotes the growth and reproduction of microorganisms in water by adding carbon sources.To achieve water purification and reuse of feed,it uses microorganisms to assimilate inorganic nitrogen and converting nitrogen compounds such as ammonia nitrogen into bacterial protein.So carbon source is an important factor affecting the construction of BFT.This study selected L.vannamei under the factory culture mode as the research object.To explore the effects of kelp residue of 50 mesh,80 mesh,150 mesh,and 200 mesh as organic carbon sources on the construction of BFT culture and water quality control of L.vannamei.By monitoring the changes of inorganic nitrogen concentration,especially the changes of total ammonia nitrogen and nitrate nitrogen.The growth performance such as feed utilization rate and specific growth rate,as well as the abundance and diversity of microorganisms in the water environment and the intestine of shrimp.The effects of seaweed residue with different particle sizes on the construction of bio-floc were investigated.The results showed that the removal efficiency of total ammonia nitrogen and nitrate conversion of 150 mesh and 200 mesh kelp residues as carbon sources were significantly higher than those of other groups.The final body weight,specific growth rate,and protein efficiency were significantly higher than those of other groups,while the feed conversion ratio was significantly lower than those of other groups.The addition of 150 meses seaweed residue as a carbon source resulted in the highest microbial diversity in the aquatic environment and the intestinal tract of shrimp,but there was no significant difference with other groups.In each group,Proteobacteria(40.78%-49.78%),Bacteroidetes(17.40%-32.23%),Actinobacteria(7.75%-14.90%)and Patescibacteria(5.62%-16.57%)still occupied the dominant position.In the common population,Rhodobacterac(27.50%),Flavobacteriac(18.11%),and Microbacteriaceae(8.36%)were dominant.Therefore,organic carbon sources with different particle sizes are important factors affecting the construction of BFT.Organic carbon sources with small particle sizes are more conducive to the construction of the BFT culture of shrimp.2.Effects of microalgal astaxanthin on shell pigmentation and nutritional value of L.vannamei in an indoor industrial aquaculture system.Blue shrimp syndrome is an important issue that needs to be overcome in indoor industrial shrimp aquaculture.Astaxanthin(Ax)is a kind of carotenoid that existed in many aquatic animals and has been found significant antioxidant activity and pigmentation effect,and the microalga Haematococcus Pluvialis has been known as the best natural source of Ax.In the present study,the effect of dietary supplement astaxanthin extracted from microalga H.Pluvialis(MAAE)on shrimp L.vannamei body pigmentation and nutritional value has been investigated in an indoor industrial aquaculture system at a production scale.The results showed that a dietary supplement of MAAE at a concentration of 20 mg/kg increased the specific weight gain rate,improved body color,and enhanced the contents of five free amino acids(Asp,Ser,Ala,Val,and His),especially the content of flavor amino acid Asp,reduced levels of fatty acids significantly,enhanced the nutritional value of the shrimp.However,there were no significant differences in muscle texture,final body weight,feed coefficient ratio,protein efficiency ratio,and weight gain.In conclusion,a dietary supplement of MAAE at relatively low doses of 20 mg/kg could improve the body color and enhance the nutritional value of L.vannamei,which indicated that it can be used as an effective nutrient enhancer for shrimp farming in an indoor industrial aquaculture system.3.Effects of microalgal astaxanthin supplementation on antioxidant capacity and resistance against Vibrio parahaemolyticus of L.vannamei in an indoor industrial aquaculture system.Experimental group MAAE(initial body weight 16.45±1.93 g)was designed to investigate the effect of adding 20 mg/kg of MAAE to the feed for 30 days on the antioxidant capacity and resistance to Vibrio parahaemolyticus infection of shrimp in indoor factory culture.Based on the study in the previous section,shrimp fed a basic blank feed(initial body weight 15.51±2.14 g)as the control group.Total antioxidant capacity(T-AOC),catalase(CAT),and superoxide dismutase(SOD)activities were measured in shrimp serum collected at the end of the culture.Attack experiments were performed using 2.0×10~9 CFU/m L of Vibrio parahaemolyticus to determine the hemocyte count,phenoloxidase(PO),alkaline phosphatase(AKP),acid phosphatase(ACP),and lysozyme(LZM)activities in the hemolymph.The results showed that the serum T-AOC,CAT,and SOD activities in the MAAE group were significantly higher than those in the control group.After the challenge,the survival rate of shrimp decreased but the MAAE group was significantly higher than the control group in 24 and 48 hours.The serum blood cell count of the MAAE group and control group increased at 12,24,and 48 hours after the challenge,but the blood cell count of the MAAE group was significantly higher than that of the control group.The activities of PO,AKP,ACP,and LZM in hepatopancreas in the MAAE group were significantly higher than those in the control group at 12,24,and 48 hours.Therefore,in an indoor factory culture system,adding a 20 mg/kg low dose of Ax into the feed can significantly enhance the antioxidant capacity and resistance against Vibrio parahaemolyticus infection of shrimp.So MAAE can be used as a choice for the prevention of the disease of L.vannamei. |
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