Effect Of Vitamin A And Vitamin E On Milk Performance, Immune Function And Ruminal Fermentation Of Dairy Cows

This experiment was conducted to study the effects of vitamin A and vitamin E on rumen fermentation, milk performance,serum hormones,apparent digestibility of nutrients in diets and antioxidant and immune function of dairy cows, in order to provide the oretical basis for addition of vitamin A and vitamin E in diet of dairy cows.The experiment was divided into 5 parts. In trial 1, sixteen health Holstein dairy cows with familiar body weight(550~600kg) were divided into 4 treatment groups with 4 replicates in each treatment,and the average dry matter intake of each cow was 17.3kg at the beginning of the experiment.The experiment was a 2×2 factorial arrangement (two VA levels and two VE levels) with total 4 kinds of diet combinations, and the ratio of concentration to forage was 42:58.The ruminal fluid samples were collected at the time point of 6h ,12h after feeding through the oral of cows on the 60d in the test, in order to study the effects of vitamin A and vitamin E on ruminal fermentation by determining the pH value,the concentrations of NH3-N,BCP,VFA in rumen liquids.The trial 2,3,4 and 5 were conducted to study the effects of vitamin A and vitamin E on milk performance,serum hormones,apparent digestibility of nutrients in diets and antioxidant and immune functions of dairy cows.The experiment was a 2×2 factorial arrangement (two VA levels and two VE levels) with total 4 kinds of diet combinations,and the ratio of concentration to forage was 42:58.Twenty-eight health Holstein dairy cows similar in weight(550~600kg) and lactation stage were randomly divided into 4 groups,with 7 in each group,and the average dry matter intake of each cow was 17.3kg at the beginning of the experiment.Pre-trial period lasted 15d and the experimental period lasted 60d.The results were showed as followed under the present experimental conditions:1. Different levels of VA and VE had no significant effects on pH value, the concentrations of NH3-N and VFA in rumen liquids. But the BCP concentration in rumen liquid was significantly increased for dairy cows supplemented with high level of VE(1.6IU/kgBW)or high level of VA(220IU/kgBW)at the time point of 12h after feeding (P<0.05).2. Adding high level of VE(1.6IU/kgBW)to the diet could obviously improve milk production(P<0.05)and the concentration of VE in milk and reduce SCC(P<0.05).3. The contents of COR and NEFA were significantly decreased, PRL and G contentrations in serum were significantly increased after adding high level of VE(1.6IU/kgBW)to the diet(P<0.05).4. The appearant digestibility of EE and CP was significantly increased for the dairy cows adding high level of VE(1.6IU/kgBW)to the diet (P<0.05), and adding high level of VA(220IU/kgBW)to the diet tended to increase the appearant digestibility of EE.5. The antioxidant function was improved for dairy cows adding high level of VE(1.6IU/kgBW)or high level of VA(220IU/kgBW)to the diet, and the concentrations of T-AOC,SOD,GSH-Px,CAT and the inhibition of hydroxyl radical were increased, and the concentration of MDA was decreased.6. The concentrations of VE and VA in serum were significantly increased for dairy cows supplemented with high level of VE(1.6IU/kgBW)in diet. Adding high level of VA(220IU/kgBW) to the diet tended to increase serum VA concentration and decrease serum VE concentration.7. The concentrations of IgM,IgG,IgA, sCD4,sCD4/sCD8,IL-1,IL-2 and TNF-a in serum were obviously increased after adding high level of VE(1.6IU/kgBW)to the diet(P<0.05).The concentrations of IgA and TNF-a in serum were significantly increased (P<0.05), and the concentrations of sCD4 andI L-2 in serum tended to increase after adding high level of VA(220IU/kgBW)to the diet8. The interaction of VA and VE had certain effects on milk performance, antioxidant and immune function of dairy cows. Under the present experimental conditions, the supplementation of VE (1.6IU/kgBW) and VA (110IU/kgBW) in diet would have better effect , and the supplementation of VE (1.6IU/kgBW) and VA (220IU/kgBW) would be better for antioxidant and immune functions of dairy cows.