| Sea cucumber(Apostichopus japonicus)is playing great importance role in mariculture industry in China because of its unique medicinal nutrition and great economic value.Nowadays,Sea cucumber aquaculture has become the leading section of coastal fisheries economy in northern China.The sustainable development of sea cucumber industry relies on safe,high quality and green formula feeds,but the advancement of study on the nutrition and feeds lags behind the culture.Thus,it is imperative to develop high quality formula feeds for intensive,environment-friendly and healthy farming.From the perspective of feed science and nutriology of sea cucumber,this study was conducted to investigate the proximate compositions of feedstuffs,the digestibility of main nutrients and nutrient requirement of sea cucumber,physiological effects of nutrition,the relationship between nutrition and immunity and optimal ratio of animal to plant(A/P)protein,plant protein sources from soybean in the diet to obtain the key feed and nutritional parameters.The results can provide scientific basis for formulating nutritional standard of sea cucumber,developing and producing sea cucumber feed in line with market demand,and promoting sustainable development of sea cucumber industry.The experimental results are listed as follows:(1)The proximate nutrient components of 14 feedstuffs for sea cucumber were determined by the method of nutrient analysis and the digestibilities of main nutrients(dry matter,protein,and lipid)in sea cucumbers with different weights were investigated by digestion experiment with slight modifications.Feedstuff with high protein(HF)included mussel meat meal,fish meal,soybean meal,spirulina meal,peanut meal and corn gluten meal.Dry matter,crude protein,crude lipid,crude fiber and ash of HF ranged 87.46%-94.36%,44.64%-64.43%,2.12%-13.855,4.37%-5.63%,3.42%-14.55%,respectively.Feedstuff with low protein(LF)included several large algae powder and beer grain.Dry matter,crude protein,crude lipid,crude fiber and ash of LF ranged 91.35%-94.13%,6.45%-25,14%,0.45%-6.45%,4.67%-27.21%,10.18%-17.48%,respectively.The digestibilities of dry matter,protein and lipid were significantly different for 14 feedstuff,which showed positive correlation with the initial weight of sea cucumbers(P<0.05).The digestibilities of dry matter,protein,and lipid ranged 30.17%-58.90%,39.73%-73.24%,and 28.24%-52.24%for LF,respectively.The digestibilities of dry matter,protein,and lipid ranged 44.90%-66.59%,58.78%-78.72%,and 40.82%-56.71%for HF,respectively.Sea cucumbers showed higher digestibilities of dry matter,protein,and lipid of fish meal(>61%,>74%,and>52%,respectively)compared with other feedstuff(P<0.05)among HF,with the exception of digestibility of mussel meat meal protein.However,the digestibilities of dry matter,protein,and lipid(30.17%,31.88%,32.52%)of the Ruppia maritime in sea cucumbers were significantly lower than those in the other feedstuffs(P<0.05)among LF.(2)The optimal requirements of protein,lipid and carbohydrate for juvenile sea cucumbers were investigated.Diets of Cornell design were formulated to contain protein,lipid and carbohydrate at different level.Results showed that growth,digestibilities of feed nutrients,digestive enzyme activity,protein metabolism-and immune-related enzymes activities were significantly affected by the level of protein,lipid and carbohydrate(P<0.05).Under the experimental conditions,the optimum nutritional requirements of protein,lipid and carbohydrate for sea cucumbers were 15%-19%,1.7%-4.7%,30%-34%,respectively.Within this range,the weight gain rate(WGR)of sea cucumbers was above 73%,and the digestibilities of dry matter,protein and lipid were higher than 51.94%,60.80%and 59.54%,respectively;protein metabolism related enzymes(glutamic-oxalacetic transaminase and glutamic-pyruvic transaminase),as well as immune related enzymes(superoxide dismutase,catalase,acid phosphatase,alkaline phosphatase)were significantly elevated.When protein,lipid and carbohydrate in feed were 16.75%,3.65%and 32.87%,respectively,the maximum weight gain and specific growth rate reached the maximum(97.15%,1.51%/day).(3)The effects of ratio of A/P protein on growth performance,digestibilities of diets and nonspecific immunity parameters of juvenile sea cucumbers were evaluated.Results indicated that diets with different ratios of A/P protein had significant effects on growth parameters of sea cucumbers(P<0.05)except body wall coefficient(BWC).When the ratio of A/P protein was 1:3,weight gain rate(WGR),specific growth rate(SGR),body wall weight(BWW)and BWC reached the maximum.The digestibilities of dry matter,crude protein and crude lipid in diets were significantly affected by the ratio of A/P protein(P<0.05).When the ratio of A/P protein was 1:2,the digestibilities of dry matter,crude protein and crude lipid was the highest.Glutamic-oxalacetic transaminase and Glutamic-oxalacetic transaminase/glutamic-pyruvic transaminase in the intestinal wall,and superoxide dismutase,catalase and acid phosphatase in the coelomic fluid were significantly affected by the ratio of A/P protein(P<0.05).while glutamic-pyruvic transaminase in the intestinal wall and lysozyme activity in the coelomic fluid were not significantly affected.(4)A culture experiment was conducted to evaluate the effects of soybean meal,soybean protein concentrate and fermented soybean meal in diets with equal nitrogen and lipid at 1:3 ratio of A/P protein on growth performance,digestive enzymes and non-specific immune parameters of sea cucumbers.Results showed that the growth parameters(WGR,SGR and BWW)of sea cucumbers fed the diet with femented soybean meal were significantly higher than those of sea cucumbers fed soybean meal and soybean protein concentrate(P<0.05).Based on the previous experimental results,six diets with different fermented soybean meal contents were designed to replace the soybean meal in the control group at 0,4%,8%,12%,16%and 20%.The effects of fermented soybean meal contents on growth performance,activities of digestive enzymes and non-specific immune parameters of sea cucumbers was evaluated through a culture experiment to obtain the optimum content of fermented soybean meal in the diet.Results showed that when the ratio of A/P protein was 1:3 and the amount of fermented soybean meal in the diet was 16%,the WGR and SGR increased by more than 57%compared with the control group;the WGR,SGR and body wall protein content were significantly higher than those of the other groups(excluding 20%fermented soybean meal group);the activities of protease,pepsin,lipase,amylase,and immune parameters(superoxide dismutase,catalase,acid phosphatase,alkaline phosphatase and total antioxidant activity)were also significantly improved?... |
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