INTRANASAL OR PARENTERAL RESPIRATORY VACCINATION UPON ARRIVAL OR DELAYED IN FEEDLOT HEIFERS
Modified-live virus (MLV) vaccines are used routinely to immunize cattle against bovine respiratory disease agents, but the route and timing of MLV administration may impact their safety and efficacy. The objective of this study was to evaluate the safety and efficacy of an intranasal or parenteral MLV administered on d 0 or 28. Three arrival blocks of heifers (initial BW = 208 kg; n = 600) were randomly assigned to treatments in a 2 × 2 factorial arrangement. The generalized complete block design consisted of 15 pens per treatment with pen as the experimental unit and 10 animals per pen. Treatments were: 1) Nasalgen 3 and Vista BVD on d 0 (NAS0); 2) Vista 5 SQ on d 0 (VIS0); 3) Nasalgen 3 and Vista BVD on d 28 (NAS28); 4) Vista 5 SQ on d 28 (VIS28). Performance, activity, and health data were analyzed using a mixed model in SAS and a subset of 3 cattle per pen were selected for antibody titer analyses with repeated measures. Body weight and blood samples were collected on d 0, 28, and 56. No differences existed for performance outcomes (P 0.19). Activity (351.4 vs 354.3 min/d) and rumination (282.6 vs 285.4 min/d) time was less (P < 0.01) for delayed vs arrival vaccinated heifers. A timing vaccine day interaction existed (P < 0.01) for BRSV- and IBRV-specific antibody titers; VIS28 had the greatest (P < 0.01) BRSV antibody titer on d 56. For IBRV antibody titer on d 28, VIS0 was greatest, NAS0 was intermediate, and VIS28 and NAS28 were least (P < 0.01). Percentage of chronically ill cattle were reduced for arrival vs delayed (1.3 vs 4.7%; P = 0.02) and tended (P = 0.06) to be less for VIS vs. NAS (1.7 vs 4.3%). Arrival vaccinated heifers had a reduction in antimicrobial treatment cost ($4.63 vs $7.31; P = 0.02). These data indicate improvement in some health outcomes for the parenteral route and arrival timing of MLV respiratory vaccination, but performance was not affected during the feedlot receiving period.