Changes Of Biochemical,immune And Antioxidant Indexes In Dairy Cows At Different Lactation Stages And Regression Analysis With Milk Composition

In this thesis,the changes of DHI,milk yield,milk composition,serum biochemical indexes,immune and antioxidant parameters of dairy cows at different lactation stages were studied,and a stepwise regression model between milk yield and milk composition and immune,antioxidant and biochemical indexes was established.The main biochemical,immune and antioxidant indexes affecting milk yield and milk composition at different lactation stages were screened,and then the health status and milk performance of animals could be predicted by corresponding indexes,which provided a reference for the formulation of early warning values for scientific evaluation of nutritional status and oxidative stress level of dairy cows.This thesis is divided into four experiments.According to the physiological characteristics of dairy cows,the first,second and third experiments selected six stages of dairy cows,namely,pre-perinatal period(21 days before delivery),post-perinatal period(21 days after delivery),pre-lactation(22 ～ 100 days after delivery),mid-lactation(101 ～ 200 days after delivery),post-lactation(201 ～ 300 days after delivery)and dry period(301 ～ 360 days after delivery),30 cows in each stage,a total of 180 cows.The changes of DHI,milk composition,milk yield,serum biochemical indexes,immune and antioxidant indexes of dairy cows at different lactation stages were studied.In experiment 4,a stepwise regression model of milk yield,milk protein rate,milk fat rate,lactose rate and somatic cell count with serum immune antioxidant and biochemical indexes of dairy cows at different lactation stages was established.The test results are as follows :(1)The milk yield of 305 was lower in the early lactation period.The peak day is lower in the late perinatal period;lactation persistence is higher in the late perinatal period;the peak day is higher in the late perinatal period;milk production is higher in the early lactation.(2)The milk fat rate was higher in late perinatal and late lactation;MUN was higher in the middle of lactation;lactose rate was higher in the early and middle lactation.(3)Serum glucose and lipid metabolism indicators : TBIL,NEFA,β-hydroxybutyric acid and TG levels were higher in the late perinatal period;the contents of LDL and HDL were higher in the middle stage of lactation.CHOL was lower in the early perinatal period,late perinatal period and dry milk period.(4)Serum protein metabolism indexes : TP and ALB contents were higher in early lactation,middle lactation and late lactation;the content of CRE was higher in late perinatal period,late lactation period and dry milk period.BUN content was higher in pre-perinatal and mid-lactation.(5)Other serum metabolic indicators : Ca and P levels were lower in the late perinatal period;the activities of AST and ALT were higher in the middle stage of lactation.ALP activity was higher in the early,middle and late lactation.(6)Serum GSH-Px,CAT activity and MDA content were higher in the late perinatal period and early lactation;the activities of T-AOC and T-SOD were lower in the late perinatal period and early lactation.Trx R is lower in the late perinatal period.(7)Serum immune indexes : the contents of TNF-α and IL-1β were higher in the late perinatal period and early lactation;the content of NO and the activity of i NOS were higher in the late perinatal period.The contents of INF-γ and Ig G were low.(8)Whey antioxidant index :-OH clearance rate was lower in the late lactation.(9)BUN and NEFA affected milk yield and milk fat percentage at the same time;TP also affected milk yield,milk protein rate and milk fat rate.GLU also affected milk yield,milk fat rate,lactose rate and somatic cell count.T-SOD affected milk yield and somatic cell count at the same time.CHOL also affects the milk protein rate and lactose rate;TG and IL-6 affected milk fat percentage and somatic cell count at the same time.TBIL affected milk fat rate and lactose rate at the same time.ALB affected milk fat rate and lactose at the same time.Ca also affects lactose rate and somatic cell count.In summary,milk yield was affected by TP,GLU,ALP,ALT,BUN,T-SOD,NEFA and IL-6;the milk protein rate was affected by IL-1β,TP,CHOL,Ig G and Trx R.The milk fat rate was affected by TG,BUN,NEFA,TP,IL-6,GLU,TBIL,ALB and TNF-α.Lactose was affected by ALB,TBIL,T-SOD,Ca,GLU and CHOL.The number of somatic cells was affected by IL-6,GSH-Px,MDA,LDL,GLU,TG,AST and Ca.