Intranasal and intramuscular commercial vaccines against respiratory viruses in steers finished in feedlot

Résumé

Bovine respiratory disease (BRD) is a condition of high incidence, especially in feedlot cattle, however, there is still no consensus on the most effective vaccine  protocol for its control. The objective was to evaluate two vaccine protocols against BRD in steers finished in feedlot and their influence on respiratory indicators and weight gains. This study included 42 ½ Angus blood steers, distributed in control, IN, and IM groups. On the IN protocol, the steers received a single vaccine dose on the day of the feedlot entrance. For the IM protocol, they received two vaccine doses, the primo vaccination was performed 21 days prior to the feedlot and the reinforcement on the day of feedlot entrance. BRD indicators, body weight gain, and serum levels of immunoglobulin-G, immunoglobulin-A, and haptoglobin were measured. At slaughter, the presence and severity of pneumonia were analyzed. IM protocol presented a lower BRD indicators and incidence of pneumonia (P=0.0004 CO and P=0.03, IN) and better performance (body weight gain and slaughter weight (P=0.05) than the other groups. IN presented more respiratory disease indicators  from on D7 and the same performance of the control group. We conclude the IM protocol was more effective for steers finished in feedlot.