Effects Of Rumen-protected Methionine Supplements In Transition Diets Of Dairy Cows On The Colostrum And Growth Performance Of Calves

Two experiments were conducted to explore the effects of rumen protected methionine(RPMet)supplementation in perinatal diets on dry matter intake(DMI)and serum biochemical immune indices of perinatal cows during calving,immune indices and growth factor content in colostrum,weight gain,biochemical and immune indices,and antioxidant capacity of calves.In experiment 1,the effect of methionine on the DMI and serum biochemical of perinatal cows and immune indices and the quality of colostrum was studied.Sixty perinatal cows were assigned to 2 groups according to a completely random design and fed with either Ctrl(basal diets)or Met(basal diets supplemented with 17 g RPMet/head)diet.DMI of the perinatal cows were collected before calving,and serum and colostrum samples were collected during calving to determine biochemical indices,immunoglobulin,growth factors and other indicators.The results showed that supplementation of RPMet significantly increased the average DMI of the perinatal cows during 21 days before calving(P < 0.05).The serum urea nitrogen(BUN)and β-hydroxybutyric acid(BHBA)in the Met group were significantly lower than those in the Ctrl group(P < 0.05).Comparing to the Crtl group,the concentration of Insulin-like growth factor 1(IGF-1),Immunoglobulin G(Ig G),Immunoglobulin M(Ig M)in colostrum were significantly higher than those in the Met group(P < 0.05).There are no significant difference found for other biochemical indices in colostrum and serum(P > 0.05).There were no significant differences in immune indicators of the perinatal cows between Met and Ctrl group(P > 0.05).However,the colostrum immune indicators and growth factors in the Met group were significantly higher than those in the Ctrl group(P < 0.05).There were no significant differences in other biochemical indexes in serum(P > 0.05).In experiment 2,the effect of methionine on the growth performance of calves was studied.On the basis of Experiment 1,12 female calves were randomly selected from each group after calving.Serum samples were collected at birth,12 h,24h,48 h,and 7d after birth to measure biochemical,immune,and antioxidant indicators.The weight at birth was measured,and weight and height of the calves were measured at2 months,3 months,and 6 months of age.The results showed that the supplementation of RPMet significantly increased the body weight and content of immunoglobulin A(Ig A)at birth and 12-hour immunoglobulin M(Ig M)of the calves compared with those in Ctrl group(P < 0.05).The body weight,height,antioxidant indices and other immune indicators showed no significant difference between the two groups(P > 0.05).In conclusion,the results suggested that RPMet supplementation could increase DMI and improve protein utilization rate and negative energy balance of dairy cows,as well as promote immune function and growth factor content in colostrum,and enhance colostrum quality.Meanwhile,RPMet supplementation can improve nitrogen balance at birth and immune function of calves.