Effects Of 2-hydroxy-4-(Methylthio)Butanoic Acid Isopropyl Ester And Rumen-protected Chlorine Chloride On Production Performance And Serum Parameters In Dairy Cows

The aim of this study was to evaluate the effects of 2-hydroxy-4-(methylthio)butanoic acid isopropyl ester(HMBi)and rumen-protected choline chloride(RPC)on milk yield,milk composition and some serum parameters in dairy cows,to explore the relation between methionine and choline,and to provide the application basis of HMBi and RPC from experiment for dairy cows.Section one:The present experiment aimed to evaluate the effects of 2-hydroxy-4-(methylthio)butanoic acid isopropyl ester(HMBi)and rumen-protected choline chloride(RPC)on milk yield,milk composition and some serum parameters in dairy cows.48 Holstein cows with similar age,parity,pregnancy time and milk production(the parity before)were randomly divided into 4 groups(8 cows of each group).Control group was fed basal diet without supplement.Treatment I was fed a diet containing 20g/d HMBi(21 days befoere parturition)and 30g/dHMBi(after parturition).Treatment II was fed a diet with the supplement of HMBi as treatment I and the supplement of 50g/d RPC(21 days before parturition and 30 days after parturition).Treatment III was fed a diet with the supplement of 50g/d RPC(21 days before parturition and 30 days after parturition).The period of this experiment was from day 21 before parturition to day 80 after parturition.Compared with the the control,milk yield of cows in treatment I,II and III was improved by 6.83kg,0.97kg and 6.46kg per day respectively(P>0.05).Milk fat was improved with HMBi plus RPC(P<0.01),and milk fat had the trend of increasing with RPC only(P=0.09).Milk protein was increased with HMBi only or HMBi plus RPC(P<0.05).HMBi decreased somatic cell count(SCC)in milk(P<0.01),HMBi plus RPC or RPC only also decreased SCC in milk(P<0.05).HMBi plus RPC or RPC only decreased TC and BHBA in serum of cows(day 14 after parturition)(P<0.05).Furthermore,BHBA was decreased by HMBi plus RPC or RPC only in cows of day 70 after parturition(P<0.01).Compared with HMBi only,HMBi plus RPC decreased blood urea nitrogen(BUN)(P<0.05).These results indicate that the addition of HMBi and RPC to cows can improve production performance and milk composition,regulate fat metabolism,ease negative energy balance of cows in perinatal period and earlier lactation.Section two:The present experiment aimed to evaluate the effects of 2-hydroxy-4-(methylthio)butanoic acid isopropyl ester(HMBi)in diets with different levels of protein and lysine on production performance and serum parameters in dairy cows.45 Holstein cows with similar age,parity,milk production and lactation time were randomly divided into 3 groups(15 cows in each group).The control group was fed basal diet without supplement.The treatment group ? was fed a diet with the supplement of HMBi.The treatment group ? was fed a low protein diet with the supplement of HMBi.The period of this experiment was 77 days.Compared with the control group,the milk yield in treatment group ? and group ? increased by 1.61kg and 0.9kg(P<0.05)respectively;the milk protein content in treatment group ? increased by 0.22 percent point(P<0.01);the lactose content in treatment group ? decreased by 0.11 percent point(P<0.05);the somatic cell count(SCC)showed decreasing trend in treatment group ?(P=0.082)and treatment group ?(P=0.074).The contents of milk fat and total solid in treatment group ? were higher than those in control group and treatment group ?(P<0.01);the content of non-fat solids in treatment group ? was higher than that in control group(P<0.05).At the end of this experiment,compared with the control group,the levels of total cholesterol(TC)and triglyceride(TG)in treatment group ? decreased by 1.43mmol/L and 0.07mmol/L(P<0.05);the content of GSH-Px in treatment group ? and group ? decreased by 115.44U/mL and 165.10U/mL(P<0.01).The level of PRL in treatment group ? was higher than that in control group and treatment group ? at the beginning of this experiment(P<0.01),but the PRL levels had no significant differences between different groups at the end of this experiment(P>0.05).These results indicate that the amino acid balanced ration with high levels of metabolizable methionine and lysine can improve the milking performance of dairy cows;the low protein-supplemented amino acids diet can improve the milk production and compositions,promote lipometabolism,maintain normal level of hormones,and improve the health of dairy cows.