Effects of Bupleurum extract on the performance and blood metabolism in heat-stressed dairy cows

This experiment was conducted to evaluate the effects of Bupleurum extract (BE) on the performance and blood metabolism in dairy cows under heat stress. Forty-eight lactating Holstein cows were randomly assigned to one of four 2.5 treatments based on their dry matter intake (DMI), milk yield, and parity. Treatments consisted of 0, 0.5, 2.5 and 5.0 g·kg-1 BE, supplemented over a trial period of 10 weeks. Supplementation of BE affected the rectal temperature, DMI, milk yield, milk protein yield, and somatic cell score of the test subjects in a quadratic manner, and the peak values were reached at a dose of 0.5 g·kg-1 BE. Milk urea nitrogen concentration, milk fat, total solid content, and blood urea nitrogen, albumin, total cholesterol, high-density lipoprotein cholesterol, and β-hydroxybutyricacid were decreased (PPP=0.05) in cows fed 2.5 or 5.0 g·kg-1 of BE. Compared to cows fed 0 or 0.5 g·kg-1 of BE, serum total cholesterol and high-density lipoprotein cholesterol levels increased in cows fed 5.0 g·kg-1 of BE. Therefore, the appropriate supplemental BE level for heat-stressed dairy cows is 0.5 g·kg-1, and the safe dosage of BE is no more than 5.0 g·kg-1 .