Influence of vaccination time relative to heifers' synchronization on infectious bovine rhinotracheitis virus antibody and stress markers responses

Objective: To characterize the influence of infectious bovine rhinotracheitis (IBR) vaccination time regarding the start of estrus synchronization on antibody titer, inflammatory reaction and oxidative stress in Holstein heifers. Methods: Twenty-four heifers (12.5 to 14.0 months old) were allocated into two experiments with 12 heifers in each, according to history of bovine herpesvirus (BoHV-1) vaccination (naïve and booster vaccinated). Heifers in each experiment were assigned to Pre-synch, In-synch and control groups. Pre-synch and In-synch groups received IBR vaccine on Day -3 and Day 5 of estrus synchronization start, respectively. Control animals remained unvaccinated but synchronized. Blood samples collected on Day 0 (day of vaccination), 7, 14 and 46 and assayed for IBR antibody titer, C-reactive protein (CRP), and total antioxidant capacity (TAC). Results: The experiments showed invariably high BoHV-1 antibody titer after vaccination with live attenuated gE deleted vaccine or polyvalent vaccines containing chemically altered BoHV-1 in all vaccinated-synchronized animals compared to the control from Day 0 to Day 46 in naïve heifers, and from Day 7 to 46 in booster vaccinated animals. In booster vaccinated animals, CRP was low in Pre-synch group on Day 7 ( P <0.05), and both synchronized groups on Day 14 and 46. TAC levels of Pre-synch and In-synch naïve heifers, and pre-synch booster heifers were lower than its control group on Day 0, and in naïve vaccinated In-synch group than booster In-synch on Day 7 ( P <0.05). Conclusions: The timing of estrus synchronization related to vaccination did not alter BoHV-1 antibody levels but affected CRP and TAC which make the animals liable for pathogen invasion and/or oxidative stress during the post-vaccinal period.