| Four different experiments were conducted to evaluate the effects of supplementary vitamin E and selenium on production performance, reproductive performance, immunity and neonatal calves.Experiment 1 Forty early or metaphase lactating Holstein cows were randomly allotted to 2 groups(control and treatment) based on parity, days in milk and milk production to investigate the effect of vitamin E and selenium on production performance. Under the circumstances of intrinsic raising management and ration, cows in treatment licked the brick enriching vitamin E and selenium ad libitum, and cows in control did not feed brick. After 90 days trail, the results showed as follow: compared with control, milk production of treatment was improved by 11.25% (P>0.05). Butterfat, Milk protein, lactose were not affected by supplementary vitamin E and selenium. Somatic cell counts in milk of treatment was significantly lower than control (P<0.05). The concentration of vitamin E and seleniumin in milk and serum of treatment was significantly higher than control (P<0.01).The incidence of mastitis was decreased by 44.3% than control (P<0.05).Experiment 2 Forty Holstein cows with similar age, parity, body weight and the expected calving period were randomly allotted into 2 treatments (control and treatment) which were used to evaluate the effects of vitamin E and selenium on reproductive performance of cows. Cows in treatment licked the brick enriching vitamin E and selenium ad libitum, and cows in control did not feed brick. Experimental period is durative 150 d, including 60 d before expected calving and 90 d postpartum. The results showed that, the content of vitamin E (P<0.05) and selenium (P<0.01) in serum of treatment cows was significantly higher than those of control cows. On the first day of estrus, 7 d after estrus, the content of reproductive hormone in serum of treatment cows significantly increased compared with control (P<0.05). Treatment had a shorter interval to first postpartum estrus than control(P<0.05). Compared with control, the interval to conception was shorter (P>0.05). Pregnancy rate at the first estrus for treatment advanced by 30.77% than control,while incidence of retained placenta, mastitis and endometritis for treatment decreased by 43.75%,61.54% and 64.29% than control, respectively. These results indicated that supplementary optimum vitamin E and selenium could significantly improved reproductive performance of dairy cows.Experiment 3 Forty Holstein cows with similar body weight and parity were randomly allotted to 2 groups (control and treatment) to evaluate the effect of vitamin E and selenium on leucocyte, Immunoglobulins (Ig), T helper (CD4+) and T-cytotoxic/suppressor (CD8+) of peripheral blood. Cows in treatment licked the brick enriching vitamin E and selenium ad libitum, and cows in control did not feed brick. Experimental stage is 60d, from 30 d before expected calving to 30 d postpartum. The results showed that the count of WBC and MON% was higher in treatment than control (P>0.05). LY% was increased by supplementary vitamin E and selenium, and the difference is significant (P<0.05). Compared with control group, the content of immunoglobulin in treatment was higher. The IgG,IgA (P<0.05) and IgM (P<0.01) were significantly higher than control. CD4+ T cells and CD4+/CD8+ in treatment were significantly higher than control (P<0.05). Compared with control group, CD8+ T cells was higher, but the difference is not significant (P>0.05). These results indicated that supplementary vitamin E and selenium could improve the immunity of peripartum dairy cattle.Experiment 4 Forty Holstein cows with similar age, parity, body weight and the expected calving period were randomly allotted into 2 treatments (control and treatment) to evaluate the effects of vitamin E and selenium on growth and immune of neonatal calves. Cows in treatment licked the brick enriching vitamin E and selenium ad libitum, and cows in control did not feed brick. Experimental period is durative 90 d, including 60 d before expected calving and 30 d postpartum. The results showed that, the content of vitamin E in serum at 12 h postpartum of treatment is significantly higher than those of control (P<0.05). At 30 d prepartum, 12 h postpartum, the content of selenium in serum of treatment significantly increased compared with control (P<0.01). The content of IgG, IgM and IgA in serum at 12 h postpartum of treatment was higher than control, but the difference is not significant (P>0.05). The content of IgG, IgM and IgA in colostrum of treatment were significantly higher than those of control (P<0.05) .Compared with control, the content of vitamin E and selenium in serum of calves from treatment at 12 h postpartum was significantly higher (P<0.01). Meantime, the content of IgG (P<0.01), IgM (P<0.05) and IgA (P>0.05) in serum of calves from treatment was higher than control. Compared with control, weight (P<0.01) and body measurement (P<0.05) of calves from treatment was significantly higher for birth. For post-birthing 30 d, weight and body measurement of calves from treatment markedly increased compared with control (P<0.01). The incidence of diseases of calves was decreased by 50% than control.
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