Effects Of Dietary Beta-Carotene Level On Growth Performance,Physiological And Biochemical Indexes Of Growing Dairy Cows

The objective of the current study was to investigate the effect of β-carotene supplementation during rearing period on the physiological,biochemical and growth performance in dairy cows.A randomized block design was adopted in this experiment.Sixty Holstein cows were assigned to β-carotene(3 g/d/cow,n=15;6 g/d/cow,n=15;9 g/d/cow,n=15)and control(without β-carotene;n=15)groups on 12 months old according to body weight(BW)and physical condition.All cows were fed with the same basal diet.The trial lasted 97 days,including a 7-day adaptation period.Blood was collected at 0days,35 days and 60 days after breeding,and the body size of the cows was measured on day 1 and 60 days after breeding,and feed samples were collected.The results found:Experiment 1:β-carotene supplementation significantly increased the content ofβ-carotene in serum(P<0.05),but had no significant effect on the content of vitamin A(P>0.05).The content of β-carotene in serum was the highest when the amount of β-carotene supplementation was 6 g/d/cow.Experiment 2:Different levels of β-carotene supplementation had no significant effect on blood biochemical indicators,cytokines(P>0.05),but Immunoglobulin increased significantly(P<0.05).The content of IgA,IgG,IgM in serum was the highest when the amount of β-carotene supplementation was 6 g/d/cow.Experiment 3:Different levels of β-carotene supplementation had no significant effect on the activity of superoxide dismutase(SOD),glutathione peroxidase(GSH-PX),and catalase(CAT)(P>0.05).But the content of malondialdehyde decreased significantly(P<0.05)Experiment 4:Different levels of β-carotene supplementation increased daily weight gain(P>0.05),conception rate,the content of LH and FSH in serum(P>0.05).Conclusion:β-carotene supplementation during rearing period significantly improves the content of β-carotene,antioxidant capacity,immunity,gestation rate and daily weight gain in dairy cows.Overall,β-carotene supplementation in the diet enhances the resistance of dairy cows to disease,which has a promotion significance in dairy cows production.