Effects Of Dietary Copper Level On Performance,Blood Biochemical Indices,Rumen Bacterial Flora And Genes Expression Related To Copper Metabolism Of Lactating Dairy Cattle

The objective of this study was to investigate the effects of dietary copper level on the performance,nutrients apparent digestibility,blood indices,rumen bacterial flora,genes expression of protein and enzyme related to copper metabolism in the liver of lactating dairy cows.60 Holstein lactating dairy cows with similar milk yield,days in milk?DIM?and parity were selected and divided into 4 groups according to the principle of random distribution.Feed grade copper sulfate pentahydrate were used as copper source.All the cattle fed the basal diet with 0?10?15 or 20 mg/kg?DM basis?in group ??dietary copper8.09 mg/kg DM?,group ??dietary copper 18.09 mg/kg DM?,group ??dietary copper23.09 mg/kg DM?and group ??dietary copper 28.09 mg/kg DM?.Each group had 15 dairy cows.The whole trial lasted for 90 days.The results showed that,1)Compared with group ?,the milk yield increased by 4.91%,6.27% and 4.78%?P<0.05?in group ?,?and ? respectively and the somatic cell count significantly decreased?P<0.01?.2)Compared with the group ?,the NDF apparent digestibility of group ? and ? was increased by 6.21% and 7.60%?P<0.05?,the ADF apparent digestibility of group ? and? was increased by 6.78% and 8.22%?P<0.05?,respectively.3)The levels of serum copper,ceruloplasmin,SOD,Cu-ZnSOD and GSH-PX were increased significantly with the increase of copper content?P<0.01?.Compared with group ?,the content of serum MDA of cattle fed with group ?,? and ? was decreased by 50.0%,60.23% and 47.08%,respectively?P<0.01?.Compared with group ?,the IgG content of cattle in group ?,?and ? was increased by 49.56%,165.56% and 90.22%,respectively?P<0.01?.4)Analysis of the indicators of copper metabolism showed that adding copper can significantly increase the fecal copper excretion,urine copper excretion and copper deposition,but the copper intake have no effect on the digestibility and deposition rate of copper.5)Compared with group I,the content of acetic acid in the rumen fluid in group II,III and IV was increased by 4.46%?P<0.05?,6.86%?P<0.01?and 6.48%?P<0.01?,respectively.The content of propionic acid in the rumen fluid decreased by 5.19%?P<0.05?,9.88%?P<0.01?and 11.97%?P<0.01?,and the ratio of acetic acid to propionic acid was increased by 10.0%?P<0.05?and 18.70%?P<0.01?and 20.87%?P<0.01?.6)As the level of dietary copperincreased,the Alpha diversity analysis index of ruminal bacterial flora increased significantly.The species abundance of group II,III and IV was significantly higher than that of group I.7)The relative abundance of species composition in the bacterial flora of the rumen fluid was analyzed from the phylum level.The Bacteroidetes,Proteobacteria,and Firmicutes were dominant phylums.Compared with group I,the relative abundance of Proteobacteria with group II,III and IV was decreased by 26.03%?P<0.01?,18.52%?P<0.05?and 23.23%?P<0.01?,respectively.The relative abundance of species composition in the bacterial flora of the rumen fluid was analyzed from the genus level.The relative abundance of Succinivibrionaceae_UCG-001 and Prevotella₁ were dominant,and the relative abundance of Prevotella₁ with group II was significantly higher than that in other groups?P<0.01?.The relative abundance of Rikenellaceae_RC9_group was significantly higher than that of other groups.The relative abundances of Treponema₂with group II and III were significantly higher than those in group I and IV?P<0.05?.8)The relative expression of copper transporter genes ATP7 B and Ceruloplasmin mRNA in dairy cows was significantly increased with the increase of dietary copper levels?P<0.01?.Compared with group I,the relative expression of COMMD1 mRNA in group II was increased by 9.0%?P>0.05?,group III and group IV were reduced by 54.0% and 78.0%?P<0.01?,respectively.9)The analysis of relative expression levels of genes containing copper-related enzymes showed that the relative expression levels of SOD1,LOX and MAOA mRNA increased significantly with the increase of dietary copper levels.Compared with group I,the relative expression levels of MAOB mRNA in group II,III and IV were reduced by 24.0%,34.0% and 60.0%?P<0.01?,respectively.Dietary supplementation with copper can improve the performance of lactating dairy cows,promote nutrients digestibility and improve the body's immunity and antioxidant capacity.Dietary supplementation with copper can improve acetic acid content of lactating cattle,reduce the content of propionic acid,increase the ratio of acetic acid to propionic acid and the relative abundance of rumen flora was also increased significantly.Dietary supplementation with copper can improve the metabolism of copper in the body and the synthesis of copper-containing proteins.Copper excretion increased with the increase of copper intake.In this experiment,the optimal content of dietary copper in lactating dairy cows is 18.09²3.09 mg/kg DM and copper intakes dose was 403.59⁵14.21 mg/d.