| The development and research of protein source is the key factor of feed industry development.Sunflower meal is rich in nutrition,low in price and stable in supply.In this experiment,the grass carp,which has the highest yield in China,was taken as the research object,and 0(FM),25%(K25),50%(K50),75%(K75)and 100%(K100)soybean meal were replaced by sunflower meal in the grass carp diet.In addition,75%(M75)and 100%(M100)soybean meal were replaced by enzymolytic sunflower meal.This experiment was conducted to investigate the effects of sunflower meal and enzymolytic sunflower meal instead of soybean meal on growth,muscle quality and intestinal health of grass carp.A total of 630 high quality grass carps with an initial body weight of(90.12±0.06)g were randomly divided into21 cages with 30 fish in each the reservoir cage.The experiment were conducted in the reservoir cages(2 m × 2 m × 2 m)for 8 weeks.The results showed as follows :1、Effects of sunflower meal instead of soybean meal on the growth and fat metabolism of grass carp.With the increase of sunflower meal replacement ratio,the weight gain rate,specific growth rate,protein efficiency ratio,C3,C4 and Ig M of grass carp were decreased,while the feed conversion ratio was increased,and the difference was significant when the replacement amount was more than 50%(P<0.05).In conclusion,under the condition of not affecting the growth performance of grass carp,sunflower meal can replace 50% soybean meal in grass carp diet.At the high substitution level,the growth performance of grass carp in the enzymolytic sunflower meal group was better than that in the sunflower meal group.The weight gain rate,specific growth rate,protein efficiency and CAT activity of the enzymolytic sunflower meal group were significantly higher than those of the non-enzymolytic group(P<0.05),and feed conversion ratio and MDA content was significantly decreased(P<0.05).On the one hand,with the increase of the replacement amount of sunflower meal,the contents of high density lipoprotein,total bile acid and triglyceride in serum of grass carp were firstly decreased and then increased,while the HDL/LDL was firstly increased and then decreased.On the other hand,the relative expression levels of fas,srebp1 and pparγ genes in liver of grass carps in the non-enzymolytic group were significantly higher than those in the control group(P<0.05).The contents of high density lipoprotein,low density lipoprotein,triglyceride and total cholesterol in enzymolytic sunflower meal group were lower than those in other groups,and the HDL/LDL value was significantly higher than that in other groups(P<0.05).The relative expression levels of dgat and lpl genes in liver of grass carp in M75 group were significantly higher than those in K0 group(P<0.05),and the relative expression of pparαgene in M100 group was significantly lower than that in K0 group(P<0.05).2、Effects of sunflower meal instead of soybean meal on meat quality of grass carp.Replace soybean meal with high proportion of sunflower meal could increase the amino acid level in muscle of grass carp.The contents of histidine,glycine,threonine,methionine and valine in muscle of grass carp increased with the increase of replacement proportion of sunflower meal,and when the replacement proportion reached 75%,the contents were higher than those in control group,but there were no significant differences(P>0.05).The contents of histidine,arginine,tyrosine,methionine,proline,isoleucine and leucine in muscle of enzymolytic sunflower meal group were all lower than those of sunflower meal group.On the other hand,compared with the sunflower meal group with the same replacement ratio,the muscle hardness,adhesion,elasticity and masticability of grass carp in the enzymolytic sunflower meal group were lower(P>0.05).With the increase of sunflower meal replacement amount,the muscle springiness of grass carp was increased,while the adhesiveness of grass carp was decreased,and the muscle adhesiveness and springiness of K75 and K100 groups were significantly different from that of K0 group(P<0.05).Compared with the sunflower meal group,the muscle hardness,adhesiveness,springiness and chewiness of grass carp in enzymolytic sunflower meal group were lower(P>0.05),the muscle adhesiveness was significantly lower than that in K0 group(P<0.05),and the springiness was significantly higher than that in K0 group(P<0.05).3.Effects of sunflower meal instead of soybean meal on intestinal health of grass carpsReplace soybean meal with high proportion of sunflower meal can damage intestinal morphology.There was no significant difference in the intestinal morphological structure indexes between the K25 group and the K0 group,but the villus height,mucosal thickness and crypt depth in the K75 and K100 groups were lower than those in the K0 group,and the villus height was significantly different(P<0.05).The height of intestinal villi in the enzymolytic sunflower meal group was lower than that in the control group and higher than that in the sunflower meal group with the same replacement ratio,but the crypt depth had no significant difference between the two groups(P>0.05).In addition,through the analysis of the intestinal microflora structure of grass carp,it was found that there was no significant difference between Shannon and Simpson in each experimental group(P>0.05).Compared with the control group,the replacement of soybean meal with sunflower meal significantly increased the intestinal flora Observed＿species,Chao1,ACE and PD values of grass carp(P<0.05).There was no significant difference in α-diversity between the sunflower meal group and the control group,but the values of Observed＿species,Chao1,ACE and Pd in the K25 group were higher than those in the control group(P>0.05).At the phylum level,the intestinal flora of grass carps was mainly composed of Proteobacteria,Firmicutes,Cyanobacteria and Bacteroidetes,and the proportion of Firmicutes in the intestinal tract of grass carps in M75 group was significantly higher than that in other groups(P<0.05),and the proportion of Proteobacteria was significantly decreased(P<0.05).Compared with the control group,the percentages of Proteobacteria and Bacteroidetes decreased after soybean meal was replaced by sunflower meal,while the percentages of Firmicutes and Cyanobacteria increased(P>0.05).The relative expression levels of il10,il-1β and iκbα in intestinal tract of grass carps were significantly decreased when the replacement ratio of sunflower meal was more than 50%(P<0.05),the relative expression levels of tlr4,il6 and nf-κbp65 were firstly decreased and then increased.Compared with the control group,the relative expression levels of il10 and il6 genes in the intestinal tract of grass carp in the enzymolytic group were significantly decreased(P<0.05),tlr4 and nf-κbp65 genes were significantly decreased in M100 group(P<0.05).The relative expression levels of il10,tlr4,il6 and nf-κbp65 in K25 group were not significantly different from those in K0 group(P>0.05),and the relative expression levels of il-1β and iκbαwere significantly higher than those in K0 group(P<0.05).With the increase of replacement proportion of sunflower meal,the relative expression levels of zo-2,occludin and claudin-b in intestinal tract of grass carp showed a decreasing trend,and the relative expression levels of zo-2,occludin and claudin-b in intestinal tract of grass carp in enzymolytic sunflower meal group were higher than those in non-enzymolytic sunflower meal group.Except for K50 and K75 groups,there was no significant difference in the relative expression of claudin-c gene between the other groups and the control group(P>0.05),K50 and K75 groups were significantly higher than K0 group(P<0.05).In conclusion,the substitution of soybean meal with sunflower meal is beneficial to improve the muscle structure,increase the amino acid content in muscle,and improve the umami and taste of muscle of grass carp.In addition,under the condition that the growth performance of grass carp is not affected,it can replace 25% soybean meal in the diet,but a large proportion of substitution of soybean meal is not conducive to the intestinal health of grass carp.Enzymolytic sunflower meal can promote lipocatabolism of grass carp,improve antioxidant capacity of grass carp,improve intestinal tissue morphology and microflora structure,and alleviate the negative effects of a large amount of sunflower meal on growth performance of grass carp. |
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