Multiple Regression Analysis On The Nutritional Status And Antioxidant Parameters In Dairy Cows

This study was conducted to investigate the changes of serum nutritional status and antioxidant parameters in different lactation stages,and a multiple linear regression model on the nutritional status and antioxidant parameters was established,which provided a reference for scientific evaluation on nutritional status of dairy cows,adjustment on dietary nutrient level and health protection.The study was divided into three experiments.The effects of different lactation stages and milk yield on serum nutritional status and antioxidant parameters of dairy cows were studied in the experiment 1 and 2.The experiments were conducted as a 2×6 factorial arrangement.The 240 healthy Holstein cows with similar weight,parity(2.08±0.465)and feeding management were randomly divided into 12 groups with 20 replicates.One of the factor is milk production,including high yield and low yield;another factor is lactation stage,including prepartum,postpartum,early-lactation,mid-lactation,late-lactation and dry period.Nutritional status indicators consist of AKP,BUN,GLU,NEFA,p-hydroxybutyrate,VA,VE,macro-element(Ca,K,Mg,P)and micro-element(Cu,Fe,Mn,Se,Zn,Cd,Co,Cr,Mo,Pb);The antioxidant parameters include CAT,MDA,T-AOC,T-SOD,GSH-Px and TrxR.On the basis of experiment 1 and 2,the multivariate linear regression model of nutritional status indicators including NEFA,?-hydroxybutyric acid,VA,VE,Se,Zn and Cu and antioxidant parameters in different stages of dairy cows were established.And the main nutritional indexes influencing the antioxidant parameters were screened out in different stages by the stepwise regression method,and the "optimal regression equation" was proposed to estimate the antioxidant capacity.Under the experimental conditions,the following results were obtained:(1)The serum BUN,P-hydroxybutyric acid,VA content and CAT activity of high-yield dairy cows were significantly higher than those of low-yield dairy cows(P<0.05),while there was no significant difference between these two groups in terms of the levels of serum AKP,GLU,NEFA,VE,mineral elements,MDA and T-AOC,T-SOD,GSH-Px and TrxR(P>0.05).(2)The content of serum Cu,Mn,Zn,Co,Mo,VE and the activity of TrxR in prepartum of dairy cows were lower,while the content of Ca,K,Pb and the activity of CAT,T-SOD,GSH-Px were higher.The level of AKP,GLU,Ca,Se,Co,VA,VE,T-SOD and GSH-Px in postpartum were lower,while the content of NEFA,?-hydroxybutyric acid,Cr,MDA and CAT were higher.The level of GLU,Cu,Se,VA,T-AOC,CAT,T-SOD and GSH-Px were lower in early-lactation,and the content of BUN,Ca,Mg,P,Fe,Cr and MDA were higher.The serum Se concentration was lower in mid-lactation,while AKP,BUN,Ca,P,Zn concentration were higher.The concentration of AKP,Fe,Se,Zn and MDA in the late-lactation were lower,GLU,Mg,P concentration and TrxR activity were higher.The level of AKP,BUN,NEFA,Zn and Mo in the dry period were lower,while the GLU content and GSH-Px activity were higher.(3)The lactation stage and milk production had significantly interaction effect on the concentration of BUN,Ca,K,Se,Zn,T-AOC,GSH-Px and TrxR in serum of dairy cows.(4)In the postpartum and early-lactation,the content of MDA had a significantly positive correlation with NEFA and ?-hydroxybutyric acid,and negative correlation with VA,VE,Se,Zn and Cu by multiple regression analysis.However,the multiple regression relationship between antioxidant parameters such as T-AOC,T-SOD,GSH-Px activity and the above nutritional indicators showed the opposite results to MDA.There was no significant multiple regression relationship between the nutritional indicators and the activity of CAT and TrxR.In summary,the nutritional status of dairy cows was significantly affected by the lactation stage and milk yield,but the antioxidant parameters were mainly affected by the lactation stage.There were significant multivariate regression relationships between the nutritional status of serum NEFA,?-hydroxybutyric acid,VA,VE,Se,Zn,Cu and the antioxidant parameters T-AOC,T-SOD,GSH-Px,MDA in the postpartum and early-lactation.