Effect Of Ruminal Protected Vitamin A On Ruminal Fermentation, Milk Performence And Immune Function Of Dairy Cows

The experiment was conducted to study effect of ruminal protected VA on ruminal fermentation, milk performance, apparent digestibility of nutrients ,immune and anti-oxidation functions of dairy cows by using in vivo test and feeding experiment, in order to confirm the reasonable dose of ruminal protected VA in diets, and provide theoretical basis for enhancing milk performance and immune functions of dairy cows.The experiment included four parts. Part 1 was a 2×2 factorial arrangement.The trial 1 choosed 16 dairy cows which were similar in weight, milk performance and parity. And those cows were randomLy divided into 4 groups, with 4 replicates in each group. Four different treatment groups were fed two kinds of treatments (NO.1 ruminal protected vitamin A, NO.2 ruminal protected vitamin A)and two levels of vitamin A(110IU/kgBW, 220IU/kgBW) in diets.Pre-trial period was 15 d and the experimental period was 60 d.;The rumen fluid was collected from the cows in different groups in the last two days during the experimental period to evaluate the effect of the different treatments and levels of vitamin A on the content of ruminal vitamin A and rumen fermentation in dairy cows.The trial 2～4 were conducted to study the effects of ruminal protected vitamin A on milk performance , apparent digestibility of nutrients in diets and antioxidant and immune functions of dairy cows. The experiments were 2×2 factorial arrangement. Four different treatment groups were fed two kinds of treatments (NO.1 ruminal protected vitamin A, NO.2 ruminal protected vitamin A)and two levels of vitamin A(110IU/kgBW, 220IU/kgBW) in diets. Twenty-eight health Holstein dairy cows similar in weight (550~600kg) and lactation stage were randomLy divided into 4 groups, 7 in each group.The ratio of concentration to forage in the diets was 42:58. Pre-trial period was 15 d and the experimental period was 60 d.The results showed as followed under the present experimental conditions:1. Two types of ruminal protected vitamin A did not have any obvious effect on the ruminal fermentation,milk production , appearant digestibility of EE,NDF, ADF, Ca ,P and CP and concentration of vitamin A in milk(P>0.05). But NO.1 ruminal protected vitamin A could improve capacity of–OH, significantly increase the activity of GSH-PX and the concentration of IL-2,TNF-αin serum. 2. Compared with the addition of 110 IU/kgBW vitamin A to the diet, the appearant digestibility of EE and the concentration of vitamin A in serum and rumen liquid were significantly increased , and the SCC was significantly decreased for dairy cows feeding high level of ruminal protected vitamin A(220IU/kgBW) in diet(P<0.05),3. Incerasing the dose of ruminal protected vitamin A in diet could improve the immune function of dairy cows, and significantly increase the concentrations of IgG, IgM, IgA, IL-1, TNF-α,sCD4 and sCD4/sCD8(P<0.05), and the concentration of sCD8 was also significantly decreased.4. Incerasing the dose of ruminal protected vitamin A in diet could improve the anti-oxidation functions of dairy cows, and could significantly increase the activity of GSH-PX, SOD,CAT, T-AOC and–OH, and the concentration of MDA was also significantly decreased.5. The supplementation of NO.1 ruminal protected vitamin A(220IU/kgBW)was the most appropriate for dairy cows under the present experimental conditions.