Effect of Dietary β-Carotene Levels on Lactating Performance of Dairy Cow

Different concentrations of β-carotene were added in the diet to investigate the subsequent effects on milk production and composition of dairy cow.Total 32 healthy Holstein dairy cows in parity 1 and lactation 200 d were selected for experiment.These cows were also with similar age,body weight and nutrition conditions and were randomly divided into 4 test groups,namely,group I as control(basal diet),group II(basal diet+ 300mg/d of β-carotene),group III(basal diet+ 600mg/d of β-carotene) and group IV(basal diets+ 900mg/d of β-carotene).The basal diet was composed of silage corn,alfalfa meals,wheat straw and concentrate.The results indicated that the adding of β-carotene to diet of dairy cow could increase lactating performance.Compared to the control group(group I),milk production and milk-protein percentage of cows from group IV increased by 11.03 % and 2.05%(P0.05),respectively.Meanwhile,milk-fat percentage of cows from group III and IV increased by 6.34% and 9.36%(P0.01),respectively.On the other hand,no significant difference was observed for the percentage of milk lactose of cows from different treatments(P0.05).