Comparative effectiveness of intranasal and parenteral vaccines for prevention of bovine respiratory disease in feedlot heifers

Objective: Our objective was to examine the effects on bovine respiratory disease (BRD) when administering a trivalent intranasal modified live virus (MLV) vaccine in conjunction with 1 of 2 different parenteral MLV respira -tory vaccines containing Mannheimia haemolytica (MH) toxoid relative to 2 vaccination protocols containing only parenteral MLV respiratory vaccine and MH toxoid. Materials and Methods: Heifers (BW = 304 +/- 5.7 kg; n = 5,240) procured from auction barns were assigned to 1 of 4 treatments at arrival processing: (1) concomi-tant administration of multivalent parenteral MLV vac-cine and a parenteral clostridial bacterin containing MH toxoid (BOV); (2) concomitant administration of multi -valent intranasal MLV, parenteral MH toxoid containing MLV bovine diarrhea virus, and parenteral clostridial bac-terin (IF3); (3) concomitant administration of multivalent parenteral MLV containing a MH toxoid and parenteral clostridial bacterin (PYR); and (4) concomitant admin-istration of multivalent parenteral MLV containing a MH toxoid, multivalent intranasal MLV, and parenteral clos-tridial bacterin (COMB). Results and Discussion: Morbidity and BRD mor-talitiy were similar across treatments. Total death loss was less in heifers that received COMB versus PYR, and BRD death loss tended to be less in COMB heifers. Growth per-formance and carcass traits were unaffected by treatment. Implications and Applications: Intranasal vaccina-tion in lieu of, or administered alongside, a trivalent MLV parenteral respiratory vaccine had no effect on morbidity or feedlot performance, thereby doing no harm. Intrana- sal vaccination alongside parenteral respiratory vaccine tended to result in lesser BRD mortality. These findings may be useful in designing arrival vaccination protocols for high-risk cattle.