Effect of vitamin D on oxidative stress indices and ram semen parameters

High vitamin D₃ receptor and vitamin D₃ metabolizing enzyme expression during spermatogenesis reflects the importance of vitamin D in fertility. This project aimed to study the effects of vitamin D3 supplementation on semen parameters and the oxidative system of rams. Twenty sexually active, mature rams were randomly selected. Rams were evenly (based on their age and live weight) categorized into four groups: control group (CG), low-dose vitamin D₃ treatment group (LDG), high-dose vitamin D₃ treatment group (HDG), and normal group (NG). The CG, LDG, and HDG were kept in a dark place for three months, and the vitamin D₃ supplement was removed from the diet to cause vitamin D₃ deficiency. The NG was placed in free sunlight, and a vitamin D₃ supplement was added to their diet; thus, the vitamin D₃ serum levels were normal in this group. After vitamin D₃ deficiency (< 75 nmol/L vitamin D in the serum), rams received 2000IU/kg vitamin D₃ in the LDG. Rams in the HDG received 20000IU/kg of vitamin D₃. The rams in the CG group did not receive vitamin D₃ supplementation. Sperm collection was performed three times in the morning for three consecutive months. The results showed a relationship between vitamin D₃ serum level, semen parameters, and oxidative stress indices. After the treatment, vitamin D₃ serum levels in LDG (128.4 ± 17.3 nmol/L) and HDG (119.3 ± 10.6 nmol/L) were statistically (P < 0.05) different from CG (42.9 ± 3.6 nmol/L). Treatment with both doses of vitamin D₃ significantly improved sperm parameters (P < 0.05). Sperm viability (95 ± 6% in LDG, 95 ± 4% in HDG, and 61 ± 1.1% in CG), sperm PMI (85 ± 5% in LDG and 84 ± 5% in HDG, whereas 51 ± 8% in CG), sperm morphology (9 ± 3% in LDG and 10 ± 2% in HDG in contrast with 28 ± 6% in CG), and DNA fragmentation index (10 ± 3% in LDG, 11 ± 1% in HDG, and 31 ± 7% in CG) were statistically different (P < 0.05). Treatment with both doses of vitamin D₃ substantially (P < 0.05) declined malondialdehyde concentration (1.2 ± 0.4 µmol/L in LDG and 1 ± 0.3 µmol/L in HDG in contrast with 9.7 ± 0.9 µmol/L in CG) and total oxidant status level (9.9 ± 3.8 µmol H₂O₂ equiv/L in LDG and 10 ± 3.6 µmol H₂O₂ equiv/L in HDG whereas 77 ± 10.6 µmol H₂O₂ equiv/L in CG). However, total antioxidant capacity concentration (4.17 ± 0.61 µmol fe²⁺/L in LDG and 4.86 ± 0.62 µmol fe²⁺/L in HDG while 1.0^2±0.29 µmol fe²⁺/L in CG) and total thiol concentration (231.9 ± 23.8 µmol/mg protein in LDG and 250.6 ± 25.9 µmol/mg protein in HDG in contrast with 31.5 ± 11.2 µmol/mg protein in CG) statistically (P < 0.05) increase in LDG and HDG. In conclusion, vitamin D₃ supplementation improved semen quality in rams by its vitamin D₃ receptor action and oxidative stress reduction.