Effects Of Body Condition On Production Performance,Plasma Metabolism And Placental Proteome Of Dairy Cows

Body condition score(BCS)is a tool widely used in dairy farms for evaluating body fat reserve,which is of great significance to the production,health and reproduction of Holstein cows.A full understanding of the impact of BCS on dairy cows is the basis for scientifically assisted management of dairy cow nutrition and production projects.In order to explore the effects of BCS on performance,plasma metabolism and placenta of dairy cows,this dissertation mainly conducts research from the following four aspects.EXP.1 Associations of body condition with subsequent calving performance,milk performance and incidence of disease in cowsA total of 1154 multiparous cows were classified on the basis of BCS(0 to 5 scale)into five groups:the BL group(BCS ≤ 3.0,n =52),the B3.25 group(BCS = 3.25,n =115),the B3.5 group(BCS = 3.5,n=371),the B3.75 group(BCS=3.75,n =224),and the BH group(BCS ≥ 4,n = 392).The results showed that increasing BCS increased the 305 days milk yield,milk fat yield,and milk protein yield first and then decreased and peaked in B3.25 group(P < 0.01).In addition,BCS was positively associated with milk fat percentage,and milk protein percentage(P < 0.01).The BH group showed the lowest calf birth weight than the other four groups(P < 0.01).It was also observed that BCS showed a correlation tendency with dystocia(P=0.082)and ketosis(P=0.063).In conclusion,prenatal over condition impairs calf birth weight,increases the risk of metabolic diseases,and reduces the subsequent milk production performance.EXP.2 Effects of different body conditions on plasma physiological and biochemical indexes of dairy cowsTwenty multiparous dairy cows with similar age,gestation length,previous 305-d mature equivalent milk yield and parity were selected.The BCS was evaluated in the close-up dry period and calving.According to BCS,the cows were divided into two groups: normal BCS group(NBCS,3.25 ≤ BCS ≤ 3.5,n = 10)and high BCS group(HBCS,BCS ≥ 4,n = 10).Plasma samples were collected on d-10,0,+3,+7,and +14 relative to calving.The results showed that the plasma NEFA and BHB concentrations of cows in the HBCS group were significantly higher than those in the NBCS group(P <0.01),and their concentrations were higher after parturition than before.The plasma leptin level in the HBCS group was significantly higher than that in the NBCS group(P = 0.03),but the BCS had no effect on adiponectin(P= 0.78)and insulin(P = 0.66)levels.The content of MDA in the plasma of cows in the HBCS group was significantly higher than that of NBCS dairy cows(P = 0.03),while BCS had no effect on the activities of GSH-Px(P = 0.96),T-AOC(P = 0.24)and SOD(P = 0.31).In addition,compared with the NBCS group,the circulating concentrations of IL-6(P = 0.04)and IL-1β(P = 0.04)in the plasma of cows in the HBCS group increased significantly,while TNF-α had a tendency to decrease(P = 0.07).The results indicating that the cows in the HBCS group had an increased risk of postpartum high-fat mobilization,higher oxidative damage,and stronger inflammation response.EXP.3 Metabolic profiling of plasma in different body condition cows using an untargeted liquid chromatography-mass spectrometry metabolomics approachSixteen multiparous dairy cows were assigned to one of two groups based on BCS: NBCS group(n= 8),and HBCS group(n = 8).Plasma samples were collected on the day of calving for untargeted liquid chromatography-mass spectrometry metabolomics analysis,and 23 differential metabolites were identified.Among these metabolites,the concentrations of six lysophosphatidylcholines and one phosphatidylethanolamine,were lower in the HBCS group than in the NBCS group(P < 0.01).Furthermore,these metabolites were involved in these four pathways,among others: glycerophospholipid metabolism,retrograde endocannabinoid signaling,autophagy,and glycosylphosphatidylinositol(GPI)-anchor biosynthesis(P < 0.05).Based on the results of the Spearman’s correlation analysis,the seven important metabolites were negatively correlated with indices of lipid metabolisms,proinflammatory cytokines,and leptin,but positively correlated with adiponectin,suggesting that these seven metabolites were significantly correlated to lipid metabolism,inflammation and over-conditioning in cows.EXP.4 TMT-based quantitative proteomic analysis of placental protein in response to different body conditionsSixteen multiparous dairy cows were divided into NBCS group and HBCS group according to BCS.Placental tissues were collected on the day of calving for quantitative proteomic using TMT.Compared with the NBCS group,the triglyceride content in the placenta of the HBCS group was significantly increased(P = 0.03),and the free fatty acid concentration had a tendency to increase(P = 0.06).We identified 576 differently expressed proteins,of which 309 were up regulated and 267 were down regulated.Furthermore,these proteins were mainly enriched in defense response,immune response,complement and coagulation cascades pathway,PPAR signaling pathway,arachidonic acid metabolism pathway and ferroptosis pathway via GO and KEGG analysis.The results showed that lipid accumulation occurred in the placenta of over-conditioning cows,and maternal obesity is associated with changes in the cow placenta proteome that correspond with increased lipid metabolism,inflammation,and metabolic dysfunction.