Production Significance of Bovine Respiratory Disease Lesions in Slaughtered Beef Cattle

SIMPLE SUMMARY: Respiratory diseases are a common health and economic problem in beef cattle production. Bovine respiratory syndrome, by which these processes are known, needs to be studied in different aspects. Therefore, this study has tried to understand the impact on the production of this disease through the study of the post-mortem lesions observed in clinically healthy beef animals and its associated factors for the management system, age and gender. It was found that there is a high percentage of subclinical pneumonia, both chronic and acute fibrinous, with different grade expanse. The animals that showed lesions experienced a lower average carcass weight than those without lesions. Furthermore, the mixed and extensive production system, as well as young animals, are associated with a greater probability of presenting pneumonic lesions. The bacterial agents were only identified in the acute fibrinous pneumonia. This study reflects the high prevalence of animals arriving at the slaughterhouse that suffer or have suffered respiratory disease and can serve as herd monitoring to adopt the necessary health measures to avoid economic losses. ABSTRACT: Bovine respiratory disease (BRD) is still a serious concern in feedlots, where it exerts a negative effect on farm productivity. There is a shortage of studies focused on the evaluation of BRD-associated lesions at the slaughterhouse in clinically healthy animals. The objective of this work was to investigate the prevalence and type of subclinical pneumonic lesions in slaughtered beef cattle, according to the age range and management system, and its impact on carcass weight. A total of 1101 beef cattle intended for human consumption were examined at slaughter. Information on age, sex, management system and carcass weight was recorded. The presence and type of pneumonia were evaluated according to gross and microscopic findings and etiological agents by PCR. Lung pneumonic lesions appeared in 17.9% of animals and were predominant among veal calves. According to the type, chronic catarrhal pneumonia prevailed in the majority of animals, and mixed and extensively reared cattle were more likely to suffer acute fibrinous pneumonia. The presence of pneumonic lesions was associated with a significant decrease in carcass weight that had more of an impact in veal male calves coming from intensive systems. Bacterial infections were the predominant infectious agent and the only cause of acute fibrinous pneumonia, while viruses were infrequent and only found in lesions with chronic catarrhal pneumonia. This study shows the importance of BRD in beef feedlots upon production values and points out the feasibility of slaughterhouse assessment of pneumonia as a method for the evaluation of BRD significance.