Effects of Selenium and Vitamin E on Performance and Blood Biochemical Indices of Dairy Cows

This study was conducted to investigate the effects of selenium(Se) and vitamin E on performance and blood biochemical indices of dairy cows.Fifty-four Holstein dairy cows(60 to 100 days after calving) were selected and assigned to nine groups by unit block method based on milk yield and parity with 6 cows in each group.There were 2 stages with 8 experimental groups and 1 calibration group per stage,and the calibration group was fixed.Se and vitamin E were added according to a 4×4 two-factor design.Supplemental levels of Se were 0,0.1,0.2 and 0.3 mg/kg,and those of vitamin E were 0,30,60 and 90 IU/kg,respectively.There was 16 diets in all,and they were represented in 0/0,0.1/0,……,0.2/90 and 0.3/90 groups,respectively.The pre-experimental and experimental periods lasted for 7 and 14 days,respectively.The performance and physiological biochemical indices of dairy cows were determined.The results showed as follows: 1) the milk yield in 0.3/0,0.2/30,0.3/30,0.1/60,0.2/60,0.3/60 and 0.1/90 groups was significantly higher than that in the other groups(P0.05);the milk fat percentage in 0/0 group was extremely significantly lower than that in 0.3/30,0/60 and 0.3/60 groups(P0.01),and significantly lower than that in the other groups(P0.05);the milk total solid in 0.3/60,0/90 and 0.2/90 groups was significantly lower than that in the other groups(P0.05);the somatic cell count in milk in 0.3/30,0.3/60,0.1/90,0.2/90 and 0.3/90 groups was significantly lower than that in 0/0,0.1/0,0/30 and 0/60 groups(P0.05).2) The serum total protein and urea nitrogen concentrations in 0.3/0 and 0.3/30 groups were significantly lower than those in the other groups(P0.05 or P0.01);the serum insulin and glucagon concentrations in 0.3/30 and 0.3/60 groups were extremely significantly higher than those in 0/0 group(P0.01);the thyroxin concentration in 0.3/0,0/30,0.3/30,0/60,0.1/60,0.2/60,0.3/60 and 0/90 groups was extremely significantly lower than that in 0/0 group(P0.01),and significantly lower than that in the other groups(P0.05);the triidiothyronin concentration in 0.3/30 and 0.3/60 groups was extremely significantly higher than that in the other groups(P0.01).3) The serum glutamic oxalacetic transaminase activity in the groups supplemented with 0 to 0.3 mg Se and 0 to 30 IU kg vitamin E and 0/60 group was significantly lower than that in the other groups(P0.05);the serum activities of glutamic-pyruvic transaminase in 0.3/60 group and glutathione peroxidase in 0.3/30 and 0.3/60 groups were extremely significantly lower than those in 0/0,0.1/0,0/30,0/60,0/90 and 0.3/90 groups(P0.01).In conclusion,the optimal levels of Se and vitamin E are 0.3 mg and 30 to 60 IU/kg,respectively.