Positive effect of organic zinc supplementation on the persistence of anti-rabies neutralizing antibodies in healthy sheep

Abstract

The main prophylactic tool to control rabies in herbivores is the systematic vaccination of susceptible animals. This study aimed to evaluate the positive effect of organic zinc (Zn) supplementation on the persistence of anti-rabies neutralizing antibodies in healthy sheep. A total of 36 Texel ewes were selected and randomly divided into 2 groups of 18 animals each. The treated group (TG) received organic Zn supplementation for 90 days, and after this period, 2 doses of rabies vaccine with a 30-day interval. The control group (CG) received the vaccine doses only and was not supplemented with organic Zn. Blood samples were collected before the first vaccination and 30, 60, and 90 days after vaccination, to determine the anti-rabies neutralizing antibody titer using the Rapid Fluorescent Focus Inhibition Test (RFFIT). The average values of anti-rabies serum-neutralizing antibodies 30 days after the first dose were 1.33 ± 0.62 IU mL-1 for the CG and 1.57 ± 0.80 IU mL-1 for the TG; 60 days after the second dose the average values were 7.60 ± 7.08 IU mL-1 and 12.97 ± 9.46 IU mL-1 for the CG and TG, respectively, with a significant difference between groups. The TG presented 100% vaccine coverage of the primary vaccination, whereas the CG presented 89.47% coverage. Oral supplementation with 75 mg organic Zn significantly increased the persistence of anti-rabies antibody titers in sheep, and it improved the vaccine coverage of the primary vaccination.