1804
Effects of supplemental bupleurum extract on blood material metabolism in heat-stressed dairy cows
This study investigated the effect of bupleurum chinense DC. extract (BE) on blood metabolism of lactating dairy cows under heat stress. Forty lactating Chinese Holstein cows (75±15 DIM, 37.5±1.8 kg of milk/d, and 1.7±0.4 parity) were randomly assigned to four groups and were individually fed a basic diet(CP = 17.2%, NDF = 53.4%) with 0, 0.25, 0.5, or 1.0 g BE/kg DM, respectively. The experiment lasted 10 weeks. Average temperature–humidity index (THI) was more than 72 throughout the experimental period. Dry matter intake was recorded twice a week. 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. Supplementation of BE increased dry matter intake (20.80, 21.61, 22.13 vs 20.91 kg/d, P = 0.02) and blood total protein (80.97, 81.08, 81.00 vs 77.22 g/L, P = 0.03) level, but decreased urea nitrogen (BUN) contents (5.65, 5.58, 5.81 vs 5.95 mmol/L, P = 0.04). Cows fed 0.25 or 0.5 g/kg BE increased albumin content (38.61, 37.53 vs 36.18 g/L, P = 0.01) compared with control cows, but BE supplementation had no effects (P > 0.05) on blood glucose (GLU), nonesterified fatty (NEFA), total triglyceride (TG), low density liporotein cholesterin (LDL-C) and high density liporotein cholesterin (HDL-C). Sodium (Na) (136.63, 134.72, 136.05 vs 137.90 mmol/L, P < 0.01) and phosphorus (P) (1.94, 1.96, 1.81 vs 2.13 mmol/L, P = 0.05) concentrations in serum were decreased by BE supplementation, while potassium (K) (3.80, 3.83, 3.90 vs 3.48 mmol/L, P < 0.01) and calcium (Ca) (2.56, 2.59, 2.66 vs 2.46 mmol/L, P < 0.01) concentrations were decerased than in controls, but BE supplementation had no effect (P > 0.05) on serum magnesium (Mg) concentration. Serum chlorine (Cl) concentration was increased in cows fed 0.5 g/kg BE (148.01 vs 140.79 mmol/L, P = 0.04) compared with control cows, and tended to be higher (144.08 vs 140.79 mmol/L, P = 0.08) in cows fed 0.25 g/kg BE, but was not affected in cows fed 1.0 g/kg BE. These findings suggest that BE supplementation could improved the protein metabolism and maintain the balance of electrolyte concentration.
Keywords: bupleurum extract; dairy cows; blood metabolism