| Experiment 1 The abnormity of flatfish is very common in seeding breeding in aquaculture,and the morphological characteristics and distribution of chromatophores,as well as skin color changes during early life history(0–72 d)of Verasper variegates were continuously observed and photographed,in order to offer reference for research and practice later.Results showed that the whole period of early development of spotted halibut lasted about 50 days in spawning water at 12–19.5 °C,and there was a rapid growing period after 20 days old.The larval melanophores occurred first and had the most contents,then xanthophores occurred,and iridophoress occurred finally.The larval cytochrome of fry body were distributed symmetrically before metamorphosis,with an increase of the melanophores density firstly and a decrease of the density followed,and the maximal density of melanophores were 1390 cells/mm2 at 9 days old.When metamorphosis occurred,the cytochrome and skin color of fry became asymmetrical.On ocular side,larval melanophores of fry body disappeared and were replaced by adult ones,and skin color was saturated and black,and the density of melanophores was stable,about 150 cells/mm2.However,on blind side,larval melanophores disappeared and no adult ones appeared,and skin color was white.In our study,albinism often occurred at metamorphosis(35 days old),and adult melanophores of ocular side were blocked,and could not pass the metamorphosis period,and became albino.Experiment 2 In this study we evaluated the contents of major nutrients including amino acids and fatty acids of two krill meals,Antarctic krill meal and hydrolyzed krill meal,and analyzed the muscle samples of five species of flatfishes,Verasper Variegates,Platichthys stellatus,Platichthys biocoloratus,Verasper moseri,and Scophthalmus maximus.The nutritional values of the two krill meals were tested with the essential amino acid index,score of ratio coefficient of amino acid,and relativity of essential amino acids,and the levels of fluorine in the two krill meals were also measured.Sixteen kinds of amino acids were found in muscles of five flatfishes,including seven essential amino acids and four flavor amino acids.The amino acid composition of muscles of the five flatfishes complied the standards of Food and Agriculture Organization of the United Nations/World Health Organization(FAO/WHO).The contents of crude proteins in Antarctic krill meal and hydrolyzed krill meal were 60.84% and 68.60% respectively,which satisfied the standards of the first class products index and the superfine products index.After hydrolysis,the content of crude proteins was significantly increased(P<0.05),whereas the content of crude lipids dropped(P<0.05).The content of ash was unaltered(P>0.05).These results suggested that there was a good balance in the amino acid composition of the two krill meals,and that the relativity of essential amino acids was similar to the fish meal.In addition,the content of fluorine in the hydrolyzed krill meal was significantly lower than that in the Antarctic krill meal(P<0.05).In conclusion,Antarctic krill meal and hydrolyzed krill meal had high nutritional values and potentially could be largely employed in aquaculture feeds.Experiment 3 A 7-week feeding trial was conducted to evaluate the effects of dietary Antarctic Krill meal(AKM)on the growth performance,blood biochemical parameters and non-specific immunity of juvenile spotted halibut(Verasper variegatus).The basal diet was formulated using fish meal,Antarctic krill meal as the main protein and fish oil and soybean oil as the lipid,respectively.A control diet(R0)without AKM,and other five diets with 8.1%(R10),16.2%(R20),24.3%(R30),32.4%(R40)and 42.5%(R50)of AKM supplementation in diets(10%,20%,30%,40% and 50% replacement of fish meal protein)were fed to six groups of 38.16±0.11 g juvenile spotted halibut.Results showed that the weight gain(WG)and feed efficiency ratio(FER)in R30 and R40 had the highest value,which were significantly higher than other groups.In addition,mortality rate(MR)in R50 was significantly higher compared with other groups(P<0.05).Total protein of R10 and R30 in serum were significant higher than other groups(P<0.05).10%-30% of krill meal levels had no significant effects on glutamicoxalacetic transaminase(GOT)and glutamicpyruvic transaminase(GPT)(P>0.05).Viscerosomatic index(VSI)and glutamate dehydrogenase(GDH)of juvenile spotted halibut had no significant difference among groups(P>0.05).Dietary krill meal levels can significantly improve the lysozyme(LZM),acid phosphatase(ACP)and alkaline phosphatase(AKP)in serum of spotted halibut(P<0.05).Above results showed that 10%~30% of krill meal levels can significantly improve growth performance,feed efficiency ratio(FCR)and non-specific immunity of juvenile spotted halibut,and 10%~30% of dietary krill meal levels had no significant effect on the function of liver and protein metabolism.Experiment 4 On the basis of experiment 3,moreover,we evaluated the effects of that Antarctic Krill meal levels on the growth,feed utilization,chemical composition in muscles and anti-oxidative capacity in spotted halibut juveniles.The results showed that supplementation of AKM in diets had a significantly effect on the chemical composition of juvenile spotted halibut.The contents of crude protein was significantly decreased while lipid and ash contents were increased with the rising AKM levels,(P<0.05).The total superoxide dismutase activity(T-SOD)and catalase activity(CAT)in serum and liver were significantly higher in AKM groups compared with the control group(P<0.05).And the contents of malondialdehyde(MDA)in serum and liver were significantly lower compared with the control group.The contents of melanophores and tyrosinase in ocular side and blind side of spotted halibut decreased significantly with the increasing AKM supplementation(P<0.05).To some extent,the feed with AKM supplementation can improve the body color of spotted halibut.In addition,moderate dietary AKM level can improve anti-oxidative capacity.Supplementation of AKM had an effect on the quality of muscles in juvenile spotted halibut,slightly.In conclusion,AKM in diets can significantly improve the non-specific immunity and body color parameters. |
PDF Full Text Request