Factors influencing infectious bovine rhinotracheitis reactivity levels through passive immunization in Jersey calves

Infectious bovine rhinotracheitis (IBR), caused by bovine alphaherpesvirus 1 (BoAHV1), is a major viral disease affecting cattle worldwide. Passive immunity from colostrum is crucial for protecting neonatal calves; however, maternally derived antibodies can interfere with vaccine efficacy, making it vital to understand their dynamics to optimize vaccination timing. This study examined the persistence of IBR-specific antibodies in 55 Jersey calves from birth to 12 weeks of age (pre-vaccination stage) and analyzed factors influencing antibody levels. Multiple linear regression analyses were conducted to evaluate the effects of dam breed, parity, IBR reactivity, gestation length, calf sex, and birth weight on IBR reactivity in calves at 12 weeks. The results revealed that Jersey calves exhibited high IBR reactivity levels at birth, which gradually declined over the 12-week period. Dam breed, parity, and IBR reactivity at calving significantly influenced calf IBR reactivity levels at 12 weeks of age (p < 0.05). Calves that received colostrum from Holstein Friesian dams, higher-parity dams, or dams with elevated serum IBR reactivity exhibited higher IBR reactivity levels at 12 weeks of age. These findings highlight the critical role of maternal factors in shaping passive immunity and underscore the need for further research into colostrum quality and antibody absorption to improve vaccination strategies.