Effects of supplemental bupleurum extract on serum hormone and immune globulin levels in heat-stressed dairy cows

Abstract Text: This experiment was conducted to evaluate the effects of bupleurum extract (BE) on serum hormone and immune globulin levels in dairy cows under heat stress. Forty lactating Holstein cows (75±15 DIM, 37.5±1.8 kg of milk/d, and 1.7±0.4 parity) were randomly assigned to one of four treatments. Treatments consisted of 0 (control), 0.25, 0.5, or 1.0 g BE/kg DM. The experiment lasted 10 weeks. Average temperature–humidity index (THI) was more than 72 throughout the experimental period. Blood samples were collected from all of animals via tail vein before the morning feeding on days 0, 21, 42, and 63. Data were analyzed by MIXED model procedure of SAS 9.2. Compared with controls, cows fed 1.0 g/kg BE had higher thyroxine (T3) (1.43 vs 1.16 ng/mL; P < 0.05) and prolactin (PRL) (230.50 vs 188.19 uIU/mL; P < 0.05) levels, and 0.5 g/kg BE had the tendence to increase the T3 (1.27 vs 1.16 ng/mL; P < 0.10) level, but 0.25 and 0.5 g/kg BE had no effect (P > 0.05) on PRL level. Serum growth hormone (GH) level was increased (2.17 vs 1.21 ng/mL; P < 0.05) in cows fed 0.25 g/kg BE compared with control cows, and tended to be higher (1.76, 1.69 vs 1.21 ng/mL; P < 0.10) in cows fed 0.5 and 1.0 g/kg BE. Supplementation of BE had decreased the cortisol (COR) levels (48.35, 49.43, 49.86 vs 64.49 ng/mL; P < 0.05), but had no effect (P > 0.05) on the levels of thyroxine, Insulin, glucagon, neuropeptide Y, leptin, insulin-like growth factor, and heat shock protein 70. Cows fed 0.5 g/kg BE increased the immunoglobulin (Ig) A content (279.25 vs 179.78 ìg/mL; P < 0.05), and IgG level was increased (36.54, 36.14 vs 27.13 mg/mL; P < 0.05) in cows supplemented with 0.25 or 0.5 g/kg BE, while the IgM and tumor necrosis factor-á (TNF-á) levels showed no difference (P > 0.05) when compared with the control cows. These findings suggest that BE supplementation could relieve metabolic disorders and enhance immune function in heat-stressed cows. Keywords: bupleurum extract;serum hormone; immune globulin