| In this experiment,we investigated the effects of replacing fishmeal with cottonseed protein concentrate(CPC)on growth,intestinal digestibility and antioxidant capacity to provide a theoretical basis for the application of cottonseed protein concentrate as a new protein source in the production of Songpu mirror carp.Cottonseed protein concentrate was used to replace fishmeal at 0,25%,50%,75% and 100%(named as CPC0,CPC25,CPC50,CPC75 and CPC100,respectively).Each group contained three replicates of 25 fish with an initial body weight of(4.17±0.02)g.The culture period was 8 weeks.The specific experimental results were as follows:(1)Effects of replacing fish meal with cottonseed protein concentrate on growth performance of juvenile Songpu mirror carpWith the increase of CPC replacement level,the weight gain rate(WGR),specific growth rate(SGR)and protein efficiency efficiency(PER)were firstly increased and then decreased,and the highest value was reached when the replacement level was 50%,and the lowest value was reached when the replacement level was 100%,and the 50% replacement level group was significantly higher than the control group and 100% replacement level group(P < 0.05).The feed coefficient(FCR)of 50% replacement group was the lowest,which was significantly lower than that of 75%replacement group and 100% replacement group(P < 0.05).With the increase of CPC replacement ratio of fish meal,the expressions of growth axis gene growth hormone(GH),insulin growth factor I(IGF1)and protein synthesis gene phosphatidylinositol 3 kinase(PI3K),rapamycin target protein(TOR)and S6 protein kinase 1(S6K)in liver and intestine were firstly increased and then decreased.And all of them were highest in 50% replacement group.In liver and intestine,the PI3 K and TOR gene expression levels of 50% replacement group were significantly higher than those of control group and 100% replacement group(P < 0.05),the AKT gene expression level was significantly higher than that of 100% replacement group(P < 0.05),and the S6 K gene expression level was significantly higher than that of other groups except 25% replacement group(P < 0.05).GH and IGF1 gene expressions were significantly higher than those in 75% replacement group and100% replacement group(P < 0.05).(2)Effects of replacing fish meal with cottonseed protein concentrate on serum biochemical indexes of juvenile Songpu mirror carpThe contents of total protein(TP)and albumin(ALB)in CPC50% replacement group were significantly higher than those in control group(P < 0.05),the contents of high density lipoprotein cholesterol(HDL-C)and glucose GLU were significantly higher than those in control group and100% replacement group(P < 0.05).The contents of low density lipoprotein cholesterol(LDL-C)and aspartate aminotransferase(AST)in 100% replacement group were significantly lower than those in 100% replacement group(P < 0.05).(3)Effects of replacing fish meal with cottonseed protein concentrate on intestinal health of juvenile Songpu mirror carpThe The activities of anterior,middle and posterior intestinal lipase increased first and then decreased,and the activities of anterior,middle and posterior intestinal lipase in 50% replacement group were significantly higher than those in other groups(P < 0.05).In foregut,amylase in 50%replacement group was significantly higher than that in other groups(P < 0.05);The protease activity in midgut and hindgut 50% replacement groups was significantly higher than that in other groups(P < 0.05).The replacement of fish meal by CPC had different effects on intestinal morphology of mirror carp.The intestinal structure of control group and 50% replacement group was orderly and the intestinal wall was intact.Between the two groups,the intestinal villi in the control group were in the best condition,with well-developed villi without fusion and shedding,relatively dense but with low villi height,while the intestinal villi in the 50% replacement group showed a small amount of fusion,relatively sparse but with the highest villi height.In the 100%replacement group,the tissue structure was the worst,the tissue microvilli were shed,a large number of intestinal villi were fused,and the shape contour was fuzzy and the height was the lowest.(4)Effects of replacing fish meal with cottonseed protein concentrate on antioxidant capacity of juvenile Songpu mirror carpThe SOD activity and glutathione peroxidase(GSH-PX)activity of intestinal tract in 50%replacement group were significantly higher than those in other groups(P < 0.05).The catalase(CAT)activity of 50% replacement group was significantly higher than that of other groups(P <0.05),and the trace reduced glutathione(GSH)content of 50% replacement group was significantly higher than that of control group(P < 0.05).The total antioxidant capacity(T-AOC)of 50% replacement group was higher than that of control group,but there was no significant difference among all groups(P > 0.05).The SOD activity and GSH concentration in liver firstly increased and then decreased,and both reached the highest values in group 50.SOD activity in50% replacement group was significantly higher than that in other groups(P < 0.05),and GSH content in 50% replacement group was significantly higher than that in 75% replacement and100% replacement groups(P < 0.05).CAT activity and GSH-PX activity in 50% replacement group were significantly higher than those in other groups(P < 0.05).With the increase of CPC replacement ratio of fish meal,the expressions of nuclear factor E2-related factor(Nrf2),copper manganese superoxide dismutase(Cu Mn SOD),catalase(CAT)and glutathione peroxidase 1b(GPX1b)of intestinal antioxidant-related genes were firstly increased and then decreased,and were the highest in 50% replacement group.The expression levels of Nrf2 gene and CAT gene in50% replacement group were significantly higher than those in other groups except 25%replacement group(P < 0.05).The expression levels of Cu Mn SOD and GPX1 b genes in 50%replacement group were significantly higher than those in other groups(P < 0.05).The CAT gene expression in 50% replacement group was significantly higher than that in control group and 100%replacement group(P < 0.05).The Kelch-like epichlorohydrin associated protein(Keap1)gene expression showed a trend of first decreasing and then increasing,and was the lowest in 50%replacement group,which was significantly lower than that in other groups(P < 0.05),and its expression was the highest in 100% replacement group.(5)Effects of replacing fish meal with cottonseed protein concentrate on anti-inflammatory ability and mechanical barrier of juvenile Songpu mirror carpWith the increase of CPC replacement ratio of fish meal,The expression levels of occludin,tight junction protein(ZO1),myosin light streptokinase(MLCK),closed protein 3(claudin3),closed protein 7(claudin7)and closed protein 11(claudin11)of intestinal tight junction protein-related genes all increased firstly and then decreased The potential was highest in 50%replacement group.The expression of occludin,ZO1,MLCK,claudin3 and claudin7 genes in 50%replacement group were significantly higher than those in the other four groups(P < 0.05).The expression of claudin11 gene in 50% replacement group was significantly higher than that in control group,75% replacement group and 100% replacement group(P < 0.05).With the increase of the proportion of cottonseed concentrate protein replacing fish meal,the expressions of intestinal proinflammatory factor-related genes interleukin 1 β(IL1 β)and interleukin(IL6)showed a trend of first decreasing and then increasing,and were the lowest in 50% replacement group.The expression level of IL1β gene in the lowest group was significantly lower than that in100% replacement group(P < 0.05).The expression level of IL6 gene in the lowest group was significantly lower than that in 25% replacement group,75% replacement group and 100%replacement group(P < 0.05).The expression level of tumor necrosis factor α(TNFα)gene in50% replacement group was significantly lower than that in CPC75 and 100% replacement groups(P < 0.05).With the increase of the proportion of cottonseed concentrate protein replacing fish meal,the expression level of anti-inflammatory factor-related interleukin-10(IL10)in intestinal cells showed a trend of first increasing and then decreasing,and the highest level was found in50% replacement group.The expression of IL10 gene in 50% replacement group was significantly higher than that in control group and 100% replacement group(P < 0.05).(6)Effects of replacing fish meal with cottonseed protein concentrate on intestinal microflora of juvenile Songpu mirror carpThe substitution of cottonseed protein concentrate also had some effect on gut flora.There were no significant differences in ace index,chao index,sobs index,shannon index and simpson index among all groups.However,compared with the control group and the 100% replacement group,the relative abundance of Firmicutes was significantly increased in the 50% replacement group,while the relative abundance of actinomyces,Proteobacteria,pontomyces and verrucococcus was significantly decreased in the 50% replacement group.In conclusion,under the conditions of this experiment,when the CPC replacement level of fish meal in the diet is 50%,the growth performance,intestinal antioxidant capacity and nutrient digestion and absorption capacity of Songpu Mirror carp can be improved.When the replacement ratio is higher than 50% and 75% to 100%,the growth,digestive ability and intestinal health of Songpu mirror carp are significantly inhibited.. |
