Effect Of Dietary Protein Level On Reproductive Performance Of Dairy Cows

According to the problem of the preparation of the nutritional imbalances of ration compound, particularly in the perinatal and peak lactateion too low or too high dietary protein levels had a adverse effect on dairy cow healthy and performance,the test used the contract test design, milk urea nitrogen, milk yield and milk composition by using contrast test of 72 Chinese-Holstein with similar age, weight, birth order, parturition date and correction lactation yield randomly divided into 3 groups, 24 in each group in north frigid area. respectively fed different protein levels diet 9.8%(A1)和13.8%(A2 ),12.6%(B1)和16.2%(B2),14.1%(C1)和17.8%(C2),that was A group(A1,A2),B group(B1,B2)和C group(C1,C2)in perinatal and peak lactation,studied the relation of dietary protein levels and BUN and the effect on related reproductive traits. Analysising for the testing results ,the test determined the appropriate dietary protein levels, and provided the basis for efficient ration compound and healthy highyield.1. The relation of dietary protein levels and BUN and the effect on milk performanceThe concentration of MUN and PUN rose significantly((P﹤0.01) with dietary protein levels rosed, A significant linear positive correlation between MUN与PUN(P﹤0.001), MUN=0.79×PUN+1.02(R2=0.91);dietary protein levels had no significant effecton milk composition(P﹥0.05)in perinatal and peak lactation;B group milk yield was significantly higher than A group (P﹤0.05), had no obvious difference with C group (P﹥0.05)in peak lactation.2. Effect of dietary protein levels on reproductive hormones of dairy cowThe concentration of LH和E2 in plasma of B and C group was significantly higher thanA group(P﹤0.05),but had no obvious difference between B and C group on 10day and 15day after delivery;the concentration of P4 in plasma of B and C group had no significant difference,but was lower than A group(P﹤0.05)5day, 10day and 15day after delivery; the concentration of E2 in plasma of B group was higher than C group(P﹤0.05)on the 20th day of estrous cycle; the concentration of P4 in plasma of A and B group had no significant difference,but was higher than C group(P﹤0.05)on the 15th and 20th day of estrous cycle.3. Effect of dietary protein levels on reproductive performance index after delivery of dairy cowThe expulsion period of afterbirth and lochia of A group was later than B and C group and difference was significant(P﹤0.05);The period of ovarian reactivation,the first estrusand the first service of C group was earlier than A group(P﹤0.05) and; the sexual period pregnancy rate of B group was highest,57.14%,respectively higher than those of A and C group 11.31% and 10.08%;the mating index of B group was lowest, 1.75%, respectively lower than those of A and C group 0.43% and 0.38%;the open period of afterbirth was significantly shorter compared with C group(P﹤0.05)and had no significant difference compared with A group.