Clinical and pulmonary ultrasound evaluations after intranasal, parenteral, or both vaccine administration for bovine respiratory disease (BRD) in dairy calves

The bovine respiratory disease (BRD) can significantly reduce the health and welfare of dairy calves. Vaccination is a common practice to minimize the incidence of BRD both intranasal and parenteral. The aim of this study was to evaluate the clinical and lung ultrasound response of calves undergoing intranasal, parenteral, or both vaccination for BRD. Two-hundred one Holstein Friesian calves were enrolled and divided into four group: control group (Group A, n=41, without vaccination); intranasal-vaccination group (Group B, n=46, intranasal vaccination); parenteral-vaccination group (Group C, n=52, subcutaneous vaccination); double-vaccination group (Group D, n=62, intranasal and subcutaneous vaccinations). All animals received a clinical examination and lung ultrasonographic evaluation at 10-15 days of life (day of recruitment: T0), 17-22 (T1), 31-38 ( T2), and 45-52 ( T3) days of life. The Kruskall-Wallis and the Dunn tests were performed to assess differences between groups and over time, while the Chi-squared test was used to evaluate the differences between proportions. All vaccinated groups showed a lower ultrasonography score over time compared to Group A except for Group B at T3. Groups B and D presented a lower percentage of diseased animals compared to Group A at T1 and T2, while groups C and D were lower at T3. The odds ratio showed a lower risk of BRD in all vaccinated groups at T1 and T2, but only Group D continued to T3. Group D also showed a lower risk compared to Group C at T1, and groups B and C at T2. The respiratory score was greater in Group C except at T3. All vaccinated groups showed similar and lower mortality compared to the control group. Our results suggest that the lung ultrasound was more effective in identifying cases of BRD. Furthermore, the association of intranasal and parenteral vaccinations was more effective in reducing the risk of BRD.