Effect Of Providing Different Levels Vitamin A On Immune Function, Lactation Performance And Reproductive Function Of Dairy Cow In Transition Period

The present study was conducted to investigate the effect of adding different levels vitamin A on immune function, lactation performance and reproductive function of dairy cow in transition period. The results provide a theoretical basis for the reasonable supplement in dietary in peripartum dairy cows.24 head of Holstein cows were selected according to the principle of 2-5 parity , body weight about 550 kg,and similar expected calving period and body condition score about 3.5 . The cows were randomly allotted to 3 groups,with 8 each group. Different groups were fed the different diets in vitamin A levels. Treatmentâ… (basic diet+55 IUVA/kgBW ) ; treatmentâ…¡(basic diet + 110IUVA/kgBW) ; treatmentâ…¢(basic diet +165IUVA /kgBW) . The basic diet was consisted of mixed pasture , silage corn and concentrated feed. The experiment lasted for 105 days, including adjustment period of 15 days and trial period of 90 days. From each cow, jugular blood samples were collected in the morning at 5 time points, 30 days and 7 days before predicted calving, and 1 day, 7 days and 30 days after calving. The blood samples were taken for physiological and biochemical indexes analysis. Milk samples were taken and investigated periodically.The study included 6 trials. The purpose of these experiments was to discuss the effect of different levels vitamin A on immune function, antioxidantive activity, lactation performance, vitamin A and RBP content in serum , reproductive function and the incidence rate of peripartum dairy cow.Under the present experimental conditions, the results showed as follows:1. The serum the number of leucocyte and immunoglobulin of cows fed the diet supplemented with 110 IU/kgBW or 165 IU/kgBW vitamin A was increased remarkably, especially , supplementation of 165IU/kgBW vitamin A is more effective to promote the immune function of dairy cow in transition period2. Supplementation of 110 IU/kgBW vitamin A in diet improved antioxidantive capacity of peripartum dairy cow.3. Supplementation of 110 IU/kgBW vitamin A in diet decreased SCC in milk, 165 IU/kgBW vitamin A group had the best effect in improvement vitamin A content of milk.4. Increasing vitamin A level in diet could increase the content of vitamin A and RBP in serum, and 165 IU/kgBW vitamin A group had the best effect.5. Supplementation of 165 IU/kgBW vitamin A in diet could promote the mature and ovulation of follicular, and was benefit to the recovery of reproductive function of dairy cow. The results of adding different levels vitamin A on indexes of reproduction cycle indicated that supplemented with 110 IU/kgBW vitamin A had the best effect.6. The incidence rate of mastitis, endometritis, retention fetal membranes and ovarian cysts of dairy cow fed the diet supplemented with 165IU/kgBW vitamin A was decreased remarkably.