Effects Of Different Levels Of β-carotene On Serum Biochemical,Immune Function And Reproductive Performance Of Dairy Cows

Twenty healthy Holstein cows of dry period with similar parity,body condition and body weight random Ly allocated in four groups,which include three treatment groups with different levels of β-carotene and one control group.The treatment groups supplied with the same diet but adding with different amount of β-carotene(0.6gβ-carotene/day/cow,1.2g β-carotene/day/cow,1.8g β-carotene/day/cow).The β-carotene supplement was given individually to the cows.The trial began feeding from the dry period of dairy cows,for 15 days of adaptation and150 days of data collection.During the experiment,cow blood samples were collected regularly.The development of uterine status of the cows was regularly detected by B-ultrasound.All indicators were used to determine the effect of different levels of β-carotene on blood metabolism,immunity function and reproductive performance of dairy cows.The results are as follows:1.Different levels of β-carotene feeding had significant effect on serum β-carotene concentration in dairy cows(P<0.05),but no significant effect on serum were observed in vitamin A concentration in dairy cows.The changes of serum β-carotene and vitamin A in dairy cows are related to each other.In generally,the serum vitamin A concentration of dairy cows decreased as the cow’s serum β-carotene concentration increased.2.No significant effect on the blood physiology,biochemical indicators,serum immunoglobulin IgA,IgG,and IgM levels(P>0.05)among treatment groups with different amount of β-carotene.However it has significant effect on the metabolic transport of β-carotene indicators,such as HDL(P<0.05).Among different treatment groups,the ratio of CD4/CD8 immune T cell subsets significant increased in the 1.2gβ-carotene added group.However,the concentration of the immunocytokines IFN-γ,TNF-α,IL-1,IL-2,IL-4 for the same group were significant decreased which showed1.2g β-carotene adding essentially benefit immune enhancement.3.The β-carotene supplement can also influence the reproductive performance of the cows.In our study,different amount of β-carotene had significant shift on reproductive hormones secretion such as estradiol and luteinizing hormone(P<0.05).The 0.6g group and 1.2g group significantly reduced the last time for the placenta lostment.Briefly,1.2g added group can promote postpartum uterus recovery and follicular development.4.The increased genetic expression of BCO1 and BCO2 in duodenum and jejunumshow they were the main absorption sites of β-carotene in intestine.