1805
Effects of nicotinamide on blood material metabolism of dairy cows under heat stress
The experiment was conducted to determine the effects of nicotinamide on the metabolism of carbohydrate, lipid, protein and the mineral of serum in heat-stressed cows under hot environment. Twenty healthy early lactation holstein cows (78.8 ± 11 DIM, 37.7 ± 1.8 kg of milk/d, 1.7 ± 0.4 parity) were randomly assigned to control and nicotinamide supplementation group. Cows were individually fed basic diet (CP=17.2%,NDF=53.4%) in control group and fed basic diet plus 8 g/d nicotinamide in nicotinamide group. The trial lasted 10 weeks. Average temperature–humidity index (THI) was more than 72 throughout the experimental period. Feed 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. There was no significant difference in dry matter intake between treatments (20.60 vs 20.71 kg/d; P > 0.05). The concentrations of nonestesterifiedfattyacid (221.25 vs 250.08 uEq/L; P = 0.03), total triglyceride (0.13 vs 0.15 mmol/L; P = 0.03), total cholesterol (5.79 vs 6.57 mmol/L; P = 0.04), and low density lipoprotein cholesterol (1.43 vs 1.76 mmol/L; P = 0.04) were decreased significantly by nicotinamide supplementation. Nicotinamide supplementation had the tendency to decrease β-hydroxybutyricacid level (0.66 vs 0.76 mmol/L; P = 0.10), but had no effect (P > 0.05) on the levels of serum glucose, total protein, albumin and urea nitrogen. Compared with control group, the levels of sodion (139.59 vs 137.90 mmol/L; P = 0.03) and chloridion ion (148.72 vs 139.75 mmol/L; P = 0.05) in serum were increased significantly by nicotinamide supplementation, but there was no difference (P > 0.05) in the levels of serum kalium, magnesium, phosphonium between the two groups. These findings suggest that nicotinamide supplementation can improved the lipid metabolism and maintain electrolyte balance of cows under heat stress.
Keywords: nicotinamide; dairy cow; blood metabolism