Antibody response, lesions, and performance do not differ between injection site (ischiorectal fossa or neck) after multivalent modified-live virus vaccination in Jersey steers

The study objective was to explore the feasibility of an alternative injection site, ischiorectal fossa (IRF), for modified-live virus (MLV) vaccination in Jersey steers. We hypothesized administration of MLV in the IRF would not cause injection site lesions and result in similar antibody response against bovine viral diarrhea virus (BVDV) compared to the neck. Jersey steers (n = 28; BW=517 ± 116 kg) were stratified by a previously assigned growth implant treatment and day-35 BVDV antibody titer and randomly assigned to 1 of 2 treatments with injection treatment equivalently represented in each of 2 pens. Treatments consisted of: 1) 2 mL MLV vaccine administered s.c. in the neck (NECK); or 2) 2 mL MLV vaccine administered s.c. in the IRF. Blood was collected on days -35, 0, 35, 70, and 105 to determine BVDV-specific antibody titers using the virus neutralization assay and BW was recorded on the same days to determine gain performance. Steers were harvested on day 106 and examined for lesions respective to injection site. Antibody titers and performance variables were statistically analyzed via a mixed model with animal as the experimental unit. Concentration of BVDV antibody increased (P = 0.05) with time, but there was no treatment difference (P = 0.94) or treatment × day interaction (P = 0.70). There was no treatment difference for BW on any day (P ≥ 0.78). There was also no treatment difference in ADG (P ≥ 0.45). However, there was a period effect, where ADG was reduced markedly (P < 0.0001) for the day 0 to 35 interim period immediately following MLV vaccination compared to day -35 to 0 (0.79 vs. 0.18 kg/d). No injection site lesions were observed during harvest and results from BVDV antibody titers and performance indicate IRF as a potential alternative route of administration for MLV vaccines.