Recent studies suggest that vitamin D may have preventive and therapeutic effects on autoimmune disease, cancer, and diabetes type 1 and 2 beyond the skeletal condition and calcium metabolism. To demonstrate the effects of an over-supplemented single 8 million I.U. Vitamin D3 IM injection on the modulation of immune responses and oxidative/anti oxidative variables in transition dairy cows. The trial was conducted on a commercial dairy farm with about 1500 lactating cows in Tehran province, Iran. Twenty four multiparous Holstein cows had been randomly categorized in control and treatment groups. In the treatment group, 12 cows received a single dose of 8,000,000 IU vitamin D intra muscularly. In the control group, placebo (distilled water) was injected to 12 cows 2 to 8 days before the expected calving time. Blood samples were collected on 21 and 7 days before calving and 1,3,7,15, and 30 days after calving. 25(OH)vitamin D3, Tumor Necrosis Factor- α (TNF-α), Interferon-γ (INF-γ), Haptoglubin, interleukin 6 (IL-6), Ferric reducing the ability of plasma (FRAP), Glutathione peroxidase (GPx), Superoxide dismutase (SOD), and hemolysate GPx were measured. This study showed that the treatment group had significantly higher amounts of 25(OH) vitamin D3, hemolysate GPx, and IL-6 values than the control group. According to our results, vitamin D injection increased the amounts of IL-6 and hemolysate GPx activity and tended to clarify the effects of vitamin D supplementation on immune and anti-oxidative modulation.

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