The Effect of Vitamin D on the Humoral Immune Response of Calves to the Sheeppox Virus Vaccine.

Introduction: Although the efficacy of the vaccine is influenced by various factors, including vitamin D levels, studies in this field have yielded different results. Vaccination with the attenuated sheeppox virus vaccine (RM/65) remains a preventive strategy in countries where lumpy skin disease (LSD) is prevalent, but there is no evidence from experimental research on the effect of vitamin D on the immune response to this vaccine for the prevention of LSD. Materials & Methods: Twenty calves were selected and divided into four groups. To ensure that calves had different baseline levels of vitamin D, they were divided into two groups. One group was exposed to sunlight, while the other two groups were kept in the shade. Each of these groups was further divided into two treatment groups: One receiving vitamin D (cholecalciferol) injections and the other a control group. All groups received the attenuated sheeppox virus vaccine (RM/65), while only two groups received vitamin D simultaneously with the vaccine. Blood samples were collected from each calf weekly for six weeks. Sheeppox virus antibodies were measured according to the World Organization for Animal Health (WOAH) protocol, with a neutralization index (NI) titer of ≥1.5 international units considered protective. Results: Statistical analysis revealed a significant increase in sheeppox virus antibody levels within individual groups after day 21 (P≤0.01). However, no significant differences were observed between the four groups beyond this time point. Consequently, antibody levels in the groups receiving vitamin D did not differ from those in the other groups. Conclusion: These findings are consistent with previous studies, indicating that vitamin D supplementation does not affect the efficacy of the vaccine.