Effects of nicotinamide on hormone levels, antioxidant status and immune function of cows in heat stressed dairy cows

Abstract Text: The experiment was conducted to investigate the effects of nicotinamide on the blood hormone levels, antioxidant status and immune function of heat-stressed dairy cows. Twenty healthy early lactation Holstein cows (78.8 ± 11.0 DIM, 37.7 ± 1.8 kg of milk/d, 1.7 ± 0.4 parity) were randomly arranged to control and nicotinamide supplementation group. Cows were fed basic diet in control group and basic diet plus 8 g/d nicotinamide in nicotinamide group for 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 56. Data were analyzed by MIXED model procedure of SAS 9.2. Compared with control cows, cows fed nicotinamide had higher contents of insulin (0.37 vs 0.34 ng/mL; P = 0.03), triiodotyronine (1.43 vs 1.27 ng/mL; P = 0.03) and leptin (2.74 vs 2.25 ng/mL; P = 0.02). Nicotinamide supplementation had the tendency to increase the thyroxine (29.02 vs 27.57 ng/mL; P = 0.08) and heat shock protein 70 (3.06 vs 2.29 ng/mL; P = 0.10), but had no effect (P > 0.05) on the contents of glucagon, insulin-like growth factor-1, growth hormone, prolactin and neuropeptide in blood. Cows fed nicotinamide had the tendency to elevate the activity of superoxide dismutase (10.29 vs 9.63 U/mL; P = 0.07), but had no effects (P > 0.05) on the activity of glutathione peroxidase, the levels of total antioxidant capacity and malondialdehyde. The contents of immunoglobulin (Ig) A (238.83 vs 160.38 μg/mL; P = 0.01), IgG (34.90 vs 21.54 μg/mL; P = 0.03), interleukin-4 (IL-4) (91.23 vs 77.19 pg/mL; P = 0.04) and IL-6 (138.81 vs 97.79 μg/mL; P = 0.01) were increased, and the ratio of CD4⁺/CD8⁺ were higher tendency (1.47 vs 1.16; P = 0.10) in cows fed 8g/d nicotinamide than in controls, while the levels of IgM, tumor necrosis factor-α, lymphocytes and the proportion of CD4⁺ and CD8⁺ T lymphocytes had no difference (P > 0.05) compared with the control. These results indicate that nicotinamide supplementation helps to alleviate the hormone metabolism disorder, improve antioxidant activity, and enhance the immune function in heat-stressed dairy cows.

Keywords: nicotinamide, dairy cows, blood metabolism