Avaliação em nível de campo de vacina para o complexo respiratório bovino em confinamento no Mato Grosso

Abstract

The Bovine Respiratory Disease Complex (BRD) is characterized by the animals' respiratory tract infection, which can be viral, bacterial origin or through the association of both. BRD has been identified as one of the most important causes of morbidity and mortality in intensive livestock, especially in young animals, causing serious economic losses with the use of medicines to treat animals and significant weight losses, directly affecting the bovine meat production chain. One of the main preventive measures carried out by the BRD is the application of vaccines to animals on arrival at the termination sites, without knowing whether the animal has already been infected by any of the agents. The present work aims to evaluate at field level the effectiveness of a commercial vaccine, as well as the frequency of positive animals through serological and antigenic techniques for different BRD agents in bulls raised in a confinement system in the state of Mato Grosso (MT); clinical and productive aspects of these since their arrival in confinement until the moment of slaughter in vaccinated and nonvaccinated animals. The study was carried out on a rural property located in the city of Ipiranga do Norte MT. 100 animals were used in the feedlot, from different properties in the midwest region of the state of MT, identified with earring and in good health. Upon arrival at the feedlot, the cattle were randomly selected and submitted to clinical examination to assess their health status and weighed. Upon arrival at the feedlot, the cattle were randomly selected and submitted to clinical examination to assess their health status and weighed. For diagnostic procedures on the day of the animals' arrival, blood samples were collected on the 21st day due to coccygeal venipuncture, in addition to a double nasal zaragatoa from each of the animals involved in the study. The samples were identified, processed and sent to the laboratory, where they were evaluated for the presence of anti-Bovine Herpesvirus Type 1 (BoHV-1) and anti-Bovine Viral Diarrhea (BVDV) antibodies using the ELISA technique of serum samples and zaragatoa; Parainfluenza Virus Type 3 (PI3) using the serum neutralization technique of serum and swab samples; and through isolation and bacteriological identification for the presence of bacterial species Pasteurella multocida, Mannheimia hemolytica and Histophilus somnie. Real-time polymerase chain reaction (qPCR) techniques were also used to detect BoHV-1, as well as ELISA to detect BVDV in possible Persistently Infected (PI) animals. At the end of the study, slaughter of the animals in a refrigerator was also observed, observing macroscopic lesions in the lungs and collecting a fragment of the organ of each bovine involved in the study for microscopic evaluation using the histopathology technique. According to the results obtained, on arrival of the animals for confinement, 100% of the animals were seroreactive for BoHV-1, 94% for PI3 and 62% for BVDV. With regard to slaughter weight, there was a difference in Daily Weight Gain (DWG) between the groups, with the animals in the treated group having a higher DWG. Regarding the macroscopic and microscopic aspects of the lungs of the animals evaluated, it was not possible to verify any difference between the groups. The results of this study pointed to the circulation of viruses of relevance to bovine health, especially in environments of intensive production such as feedlots. The detection of antibodies against the agents, as well as the specific verification of pathogens, increases the need for epidemiological surveillance and prevention of CRB-related agents from the properties related to the reproduction and production of calves. Thus, the use of vaccines would be an efficient way to avoid possible contamination and the development of clinical conditions in the adult phase of the animal.