Effect of Interferon on Feedlot Cattle

Abstract

There was no significant difference in mortality between vaccinated and control calves. However, vaccination delayed death; the earliest deaths occurred among control calves. Ninety-six calves seronegative for I BR virus antibody were vaccinated and 82 of 86 (95.3%) of the survivors seroconverted within 14 days. Only 2 of 84 surviving control calves developed antibody to IBR virus by 14 days. Most vaccinated calves tested developed intranasal IFN after vaccination. Interferon was detected in many unvaccinated calves without evidence of IBR virus infection. Twenty-seven calves had IFN present in the NS at the time of vaccination. Twenty of these calves survived and seroconverted to IBR virus by 14 days after vaccination. This intranasal vaccine was effective on seronegative cattle with known intranasal IFN titers during a shipping fever outbreak.