Effect Of Methionine Hydroxy Analogue Isopropyl Ester (HMBi) On Lactation Performance,Reproduction Performance And Serum Parameters In Dairy Cows

As high-yield ruminants,dairy cows are affected by many factors in their production performance,reproductive performance and serum biochemical indicators.Studies have found that methionine is one of the main restrictive amino acids in dairy cows;HMBi is an esterification product of HMB with isopropanol and is a new high-potency source of methionine in dairy cows.In the preliminary experiment,our laboratory found that adding a certain amount of HMBi to the TMR of dairy cows increased the milk production of dairy cows and improved the milk composition,which is related to the amount and time of addition.Therefore,in this experiment,60 g HMBi was added to the diet of 14-month-old dairy cows to explore the absorption and changes of the methionine hydroxy analog isopropyl ester in dairy cows;according to the test results,25 g/d HMBi was added to the pre-perinatal TMR.Exploring the effects of HMBi on the health of perinatal dairy cows and the milk performance and reproductive performance in the pre-lactation period.It is expected to provide experimental basis for the application of HMBi in dairy cow production.This test is divided into 2 parts:Experiment 1 The effect of HMBi on serum free amino acids,serum proteins and antioxidant parameters of 14-month-old dairy cows6 healthy 14-month-old dairy cows randomly divided into a control group and a experimental group,（3 cows each group）.The control group was fed with cattle farm TMR.On the basis of the control group,the experimental group was supplemented with 60 g HMBi per cow.Blood was collected from the tail vein at 0,3,6,9,12,18 h after feeding,and the free serum was determined.Measuring the changes of free amino acid concentration in serum,serum protein and antioxidant parameters.The results showed that diet supplementation of 60 g HMBi increased the serum methionine content within 18hours,and affected the changes of other amino acid concentrations to varying degrees;within 18 hours,it had no significant effect on serum TP and ALB（P>0.05）;12 h significantly increased GLB content（P<0.05）;3 h,9 h,12 h extremely significantly increased BUN content（P<0.01）,6 h significantly increased BUN content（P<0.05）;3 h,18 h extremely significantly reduced Serum TAA content（P<0.01）,9 h,12 h significantly reduced serum TAA content（P<0.05）;3 h extremely significantly reduced serum GSH-Px activity（P<0.01）,12 h significantly reduced GSH-Px activity（P<0.05）;3 h significantly reduced SOD activity（P<0.05）,6 h,9 h extremely significantly reduced SOD activity（P<0.01）;6 h,12 h significantly reduced T-AOC（P<0.05）,9 h extremely significantly reduced T-AOC（P<0.01）;it had no significant effect on the content of MDA in serum.The results showed that diet supplementation 60 g of HMBi increased the content of methionine and albumin in the serum,however,it causeed lipid peroxidation in the liver of dairy cows and reduced the activity of antioxidant enzymes.It shows that HMBi has a high biological potency and can increase the methionine content in the serum,but the amount should not be too much.Experiment 2 The effect of HMBi on Lactation performance,reproduction performance,serum protein,serum antioxidant and fat metabolism parameters in dairy cowsOn the basis of test 1,according to age（3.45±0.23）years,parity（1.15±0.17）fetus,and days after mating（251.55±6.95 d）,40 healthy cows were selected and randomly divided into control group and experimental group,each with 20 cows.From the pre-perinatal period,the control group was fed the cattle farm TMR.On the basis of the control group,the experimental group added 25 g/d of HMBi to each cow.The experimental period started from 21 days before delivery and ended at 80 days after delivery.The results showed that:1)Dietary supplementation of 25 g/d HMBi significantly increased the milk yield and milk urea nitrogen（MUN）of dairy cows 1-30 days after delivery（P<0.05）,but had no significant effect on other milk components（P>0.05）.At the same time,it significantly increased the milk yield and lactose rate from 31-60 days postpartum（P<0.05）,significantly reduced the number of somatic cells（P<0.01）,and had no significant effect on other milk components（P>0.05）.2)Adding 25 g/d HMBi to the diet significantly increased the content of serum globulin（GLB）,total protein（TP）,and serum urea nitrogen（BUN）in dairy cows 30 days postpartum（P<0.05）,and for albumin（ALB）,Total amino acid（TAA）had no significant effect（P>0.05）.At the same time,it significantly increased the content of ALB,GLB,TP,BUN in the serum 60 days postpartum（P<0.05）,and had no significant effect on TAA（P>0.05）.3)The addition of 25 g/d HMBi in the diet significantly increased the glutathione peroxidase（GSH-Px）and superoxide dismutase（SOD）activities and the total antioxidant capacity（T-AOC）in the serum of dairy cows 30 days postpartum（P<0.05）.It significantly reduced the content of malondialdehyde（MDA）,lactate dehydrogenase（LDH）activity（P<0.05）;at the same time significantly increased the content of GSH-Px,SOD and T-AOC in serum at 60 days postpartum（P<0.05）,significantly reduced the content of MDA（P<0.05）,and LDH had no significant effect（P>0.05）.4)The supplementation of 25 g/d HMBi significantly increased the serum follicle stimulating hormone（FSH）content in dairy cows 30 days postpartum（P<0.05）,and FSH at 60 days postpartum had no significant effect（P<0.05）;females at 30 d and 60 d postpartum Diol（E₂）had no significant effect（P<0.05）;it significantly increased the birth weight of offspring calves（P<0.01）;the total conception rate of postpartum dairy cows,the first estrus conception rate,and the estrus conception rate had increased Trends,the breeding index had a decreasing trend,and the incidence of postpartum diseases such as infertility,metritis,and toxemia of pregnancy had a decreasing trend.5)The supplementation of 25g/d HMBi significantly increased the total cholesterol（TC）content（P<0.05）of dairy cows30 days postpartum,and significantly reduced the content of triglycerides（TG）（P<0.05）.Low-density lipoprotein（LDL-C）and high-density lipoprotein（HDL-C）had no significant effect（P>0.05）;significantly reduced the content of HDL-C and TG at 60 days postpartum（P<0.05）,and had no significant effect on LDL-C and TC.Therefore,diet supplementation 25 g/d of HMBi improved production performance,reproduction performance and antioxidant capacity,reduced the incidence of postpartum diseases,improved liver fat metabolism,and increased body fat utilization.It shows that HMBi can be used as an additive for long-term use in dairy cow production.