| The effects of different levels of Spirulina on growth,immunity,antioxidant capacity and body color of Cyprinus carpio were studied.360 Cyprinus carpio with a body mass of（3.01±0.10）g were randomly divided into 4 groups,with 3 repetitions in each group and 30 tails in each repetition.The basic feed（control group）and the experimental feed supplemented with60mg/g,80mg/g and 100mg/g Spirulina were fed respectively.After feeding for 4W,samples were taken for testing.The results show that:The weight gain rate,specific growth rate,feed coefficient,plumpness,liver body ratio and visceral body ratio of Cyprinus carpio in L6,L8 and L10 groups had no significant changes compared with the control group（P>0.05）;The white blood cells,red blood cells,hemoglobin and red blood cell backlog in blood showed an upward trend with the increase of Spirulina addition level.The white blood cells,red blood cells and hemoglobin in L6 group,L8 group and L10 group were significantly higher than those in the control group（P<0.05）,and the red blood cell backlog in each group did not change significantly（P>0.05）;The levels of triglyceride and total cholesterol in serum decreased first and then increased with the increase of Spirulina addition level.The levels of triglyceride and total cholesterol in L6group,L8 group and L10 group were significantly lower than those in the control group（P<0.05）,but there was no significant change in L6 group,L8 group and L10 group（P>0.05）;There were no significant changes in serum low density lipoprotein cholesterol,high density lipoprotein cholesterol,alanine aminotransferase and aspartate aminotransferase compared with the control group（P>0.05）;The content of total cholesterol in liver decreased first and then increased with the increase of Spirulina addition level.Compared with the control group,the content of total cholesterol in L6 group,L8 group and L10 group was significantly lower than that in the control group（P<0.05）,and reached the lowest value in L8 group;There were no significant changes in triglyceride content,low-density lipoprotein cholesterol content,high-density lipoprotein cholesterol content,alanine aminotransferase activity and aspartate aminotransferase activity compared with the control group（P>0.05）.The contents of serum immune indexes Complement 4 and immunoglobulin M decreased first and then increased with the increase of Spirulina addition level.Compared with the control group,the contents of complement 4 and immunoglobulin M in L6 group,L8 group and L10 group were lower than those in the control group（P<0.05）,and reached the lowest value in L8 group.Compared with the control group,the total OTU number,Chao1 index and Shannon index of L6 group,L8 group and L10 group decreased,and the Simpson index increased,indicating that Spirulina can reduce the diversity and relative abundance of intestinal flora.At the phylum level,with the increase of Spirulina addition level in the feed,the relative abundance of intestinal flora changed,in which the relative abundance of Proteus decreased gradually,the abundance of Firmicutes and dephosphorization Vibrio decreased first and then increased,the relative abundance of spirochetes,Clostridium and actinomycetes increased first and then decreased,and the relative abundance of flexor viridis and verruca increased gradually.With the increase of Spirulina addition level,Aeromonas,spirochetes and Acetobacter first increased and then decreased,Mycoplasma first decreased and then increased;Zor0006,walleria and solanacearum decreased gradually;Staphylococcus did not appear in L6 group,but in control group,L8 group and L10 group,and the abundance of L8group>L10 group>control group;Erythrobacilli appeared in the control group,but not in L6,L8 and L10 groups.The total antioxidant capacity,catalase activity and superoxide dismutase activity of Cyprinus carpio increased first and then decreased with the increase of Spirulina addition level,and the content of malondialdehyde decreased first and then increased.Compared with the control group,the superoxide dismutase activity in L6 group,L8 group and L10 group was significantly higher than that in the control group（P<0.05）,and reached the highest value in L8 group.There was no significant difference in total antioxidant capacity,catalase activity and malondialdehyde content among the groups（P>0.05）.In the white skin of Cyprinus carpio,with the increase of Spirulina addition level,the brightness l of white skin increased first and then decreased.Compared with the control group,l in L6 group was significantly lower than that in the control group（P<0.05）,and l in L8group and L10 group was significantly higher than that in the control group（P<0.05）;There was no significant difference in the red degree a*and yellow degree b*of white skin in each group（P>0.05）.In red skin,with the increase of Spirulina addition level,red skin a*and b*increased first and then decreased.Compared with the control group,a*and b*in L6 group,L8 group and L10 group were significantly higher than those in the control group（P<0.05）,and L8 group was significantly higher than those in L6 and L10 group（P<0.05）;There was no significant difference in red peel l among the groups（P>0.05）.Compared with the control group,the contents of carotenoids and astaxanthin in L6group,L8 group and L10 group were significantly higher than those in the control group（P<0.05）,and the contents of carotenoids and astaxanthin in L8 group were significantly higher than those in L6 group and L10 group（P<0.05）;There was no significant difference in the contents of carotenoids and astaxanthin in the intestine（P>0.05）;Compared with the control group,the contents of carotenoids and astaxanthin in L6,L8 and L10 groups were significantly higher than those in the control group（P<0.05）;Compared with the control group,the contents of carotenoids and astaxanthin in L6,L8 and L10 groups were significantly higher than those in the control group（P<0.05）;Compared with the control group,the contents of carotenoids and astaxanthin in L6,L8 and L10 groups were significantly higher than those in the control group（P<0.05）,and there was no significant difference in the content of pteridine（P>0.05）.Compared with the control group,the expression of gene SPR in L8 group and L10group was significantly lower than that in the control group（P<0.05）,and there was no significant change in L6 group compared with the control group（P>0.05）;There was no significant change in the expression of GCH1 gene（P>0.05）;The expression of scarb1 in L8group was significantly higher than that in the control group（P<0.05）,and there was no significant difference between L6 group and L10 group（P>0.05）;Compared with the control group,the expression of CD36 gene in L6 group,L8 group and L10 group was significantly higher than that in the control group（P<0.05）,and that in L6 group was significantly lower than that in L8 and L10 group（P<0.05）.Conclusion:under the experimental conditions,the addition of spirulina to the feed can improve the growth performance,change the intestinal flora,improve the antioxidant capacity and improve the body color of Cyprinus carpio.There were also differences among different addition groups.In general,the effect was the best when the addition level of Spirulina in Cyprinus carpio feed was 80mg/g. |
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