Effects of bupleurum extract on performance and health status in heat-stressed late lactation dairy cows

Abstract Text: This study was conducted to investigate the effects of bupleurum extract (BE) on performance and health status in heat-stressed Chinese Holstein dairy cows. Forty lactating cows (days in milk = 207.98±12.2; average milk yield = 30.96±3.96 kg/d; parity =1.96±1.07) were randomly assigned to 1 of 4 treatments according to a completely randomized block design. Cows were individually housed in pens and fed ad libitum three times daily. Treatments consisted of 0, 0.5, 2.5 or 5% BE of dry matter (CG, LG, MG or HG).The experiment lasted for 11 weeks in hot summer. Ambient temperature and relative humidity were recorded daily (0600, 1400, and 2200). Milk yields, dry matter intake (DMI), respiration rates (RR) and rectal temperatures (RT) were recorded twice a week and milk samples were collected twice a week. Blood was collected in evacuated tubes via caudal venipuncture at 0, 3, 6, 9, 11 week. Data were analyzed by repeated measures using Proc Mixed procedure of SAS 9.2. During the experiment, average temperature-humidity index were 76.8 ± 6.3, 82 ± 6.54 and 78.3 ± 6.1 respectively at 0600h, 1400h and 2200h. There was no treatment effect on RR, RT, DMI and milk yield, while the values of DMI (19.41, 19.04, 18.61 vs. 19.19 kg/d) tended to decrease with increasing dose. Milk urea nitrogen in MG was lower (12.06 vs. 12.92 mg/dL, P<0.05) than that in CG, while contents of milk fat, milk protein, lactose, total solids and somatic cell counts were not significantly affected (P>0.05). The mean corpuscular hemoglobin in HG was lower than that in CG (16.56 vs. 16.98 pg, P<0.05). The Mean corpuscular hemoglobin concentration (346.35, 347.81, 344.87 vs. 351.28 g/L, P<0.05) was decreased due to BE supplementation. No significant difference in the number of leukocytes, red blood cell count, hematocrit, lymphocytes, mean corpuscular volume, mean platelet volume and red blood cell distribution width were detected among groups. There was no treatment effect on glutamic-pyruvic transaminase, glutamic oxalacetic transaminase, globulin, albumin, total protein and alkaline phosphatase. These results indicate that BE supplemented with high dose of 5% had no negative effect on the performance and health status in heat stressed late lactation dairy cows, and 5% is safety dose.

Keywords: bupleurum extract, performance, health status