Dietary Crude Protein Level on Growth Performance and Blood Biochemical Indicators of Holstein Cows

The purpose of this test is to study the effect of dietary crude protein on growth performance and blood biochemical parameters of 140 ~ 200kg Holstein cows.21 healthy Holstein cows(body weight,142.58 ± 1.50 kg) were randomly divided into three groups with 7 duplicates per group.Dietary energy level of three diets was 12.82 MJ / kg DM.Crude protein levels were separately 16.10%,15.10% or 14.11% of DM.The results showed as follows: Dietary crude protein has significantly effect on body weight growth.The body weight growth was highest for the cows fed middle crude protein diet,significant higher than that fed high crude protein diet(P0.05),but had no significant difference with cows fed the low crude protein diet(P0.05).The total weight gain in the highprotein group,and low-protein group were lower 10.21%,5.21% than that of the middle group.The trend of the body measurement indicators is similar to the weight growth.Dietary crude protein levels had no significant effects on the serum total cholesterol,blood urea nitrogen,and β-hydroxybutyrate levels(P0.05) had significant effects on the contents of glucose,non-esterified fatty acids(NEFA) in serum(P0.05).In the present experimental conditions,the diet with DE at 12.82 MJ / kg DM and crude protein at 15.10% DM could meet the nutrient requirement of 140 ~ 200kg Holstein cows.