Efficacy of a new multivalent vaccine for the control of bovine respiratory disease (BRD) in commercial fattening units
Bovine respiratory disease (BRD) is the most common cause of morbidity and mortality in cattle. The effects of BRD are most marked during the first weeks after arrival in calf-rearing units. Vaccination is a tool that can help to control the disease by reducing both the incidence itself and the massive use of antibiotics. Recently, a new multivalent vaccine (DIVENCE(R)), containing live gE/tk double-gene deleted BoHV-1, live-attenuated BRSV, inactivated PI3, BVDV-1 recombinant protein and BVDV-2 recombinant protein, has been designed to protect cattle against the main viral pathogens associated with BRD. The aim of this study was to demonstrate the efficacy of DIVENCE(R) against BRD in field conditions. A total of 360 animals from three different batches were included in the study: one batch of 108 Holstein-Friesian males (Farm 1), another batch of 99 Holstein-Friesian males (Farm 2), and 153 Belgian-Blue cross males and females (Farm 3). On each feedlot, a single batch of animals was included in the study, with a mean age of approx. ten weeks (73.4{+/-}0.6 days). On the vaccination day (Day 0 of the study; D0), calves from the same batch were randomly distributed between the two study groups. The vaccinated group (n=183) received the DIVENCE(R) vaccine and the control group (n=177) received a placebo injection of phosphate-buffered saline (PBS) solution. Both groups were given two intramuscular doses (2 mL/dose) of the corresponding product three weeks apart. All animals were monitored during the entire fattening period (approx. 9 months) after vaccination to assess the incidence, severity, and morbidity of BRD as well as administered treatments and feed performance. Overall, vaccinated animals had significantly (p<0.004) lower morbidity than controls, with only 49 out of the 183 vaccinated calves (26.78%) presenting at least one episode of respiratory disease (RD), versus 73 out of the 177 control calves (41.24%). Thus, a reduction of 35.1% in morbidity was observed in the vaccinated animals. In terms of RD cases, vaccinated animals had a significantly (p<0.001) lower number of cases than control animals, with only 66 cases reported in the 183 vaccinated calves (0.36 cases/calf) versus 110 cases in the 177 control calves (0.62 cases/calf). A reduction of 42% in cases was observed in the vaccinated animals. During the study follow-up, a BRSV outbreak was reported in one of the farms (Farm 1) on Day 23, just two days after the second dose. The vaccinated group had significantly (p<0.02) lower morbidity (11 animals out of 54; 20.4%) and severity (score of 1.70) compared to the control group (29 animals out of 54; 53.70% and score of 2.11). Overall, vaccinated animals needed significantly (p=0.01) fewer antimicrobial treatments (at least one due to RD) than controls. Furthermore, vaccinated animals presented numerically higher average daily weight gain (p=0.07) and significantly higher carcass weight (p=0.01) than controls, at 35.78 g/day and 6.58 kg, respectively. Vaccination with DIVENCE(R) at the beginning of the fattening period decreased the incidence and morbidity of BRD following a BRSV outbreak only two days after the primary vaccination scheme. Additionally, the incidence and morbidity of BRD throughout the entire fattening period was reduced in the vaccinated animals. Thus, DIVENCE(R) can improve economic outcomes in fattening units by reducing antibiotic treatments and enhancing performance.