Seasonality of bovine respiratory disease and mitigation techniques used in receiving beef cattle in the last 10 years: a meta-analysis.

Abstract

Despite recent advances in technology and biological, nutritional, and pharmaceutical products designed to mitigate disease, bovine respiratory disease (BRD) remains the leading cause of feedlot morbidity. The objectives were to (1) quantify the effects of BRD interventions that have been reported in the literature within the United States for the previous decade, and (2) to investigate seasonal effects on BRD incidence. A detailed literature search was conducted using Preferred Reporting Items for Systematic Reviews and Meta-analyses methods. A total of 103 records (56 studies) met criteria by providing percentages of cattle treated at least once for BRD and reporting a control. Available data were extracted from each study for control groups and treatment groups and a logs risk ratio of both metrics (ai = controlBRD, bi = controlHealthy, ci = treatmentBRD, di = treatmentHealthy) was calculated for each record using the escalc function in the R package metafor (v4.8) in R (v4.5). A multi-level meta-analytical (MLMA) model was used to determine overall effects on BRD morbidity because data non-independence existed. The MLMA model yielded a pooled estimate for log ratios of 0.07 (P = 0.09) and indicated the presence of heterogeneity (Q = 336, P < 0.0001), suggesting that BRD incidence tended to decrease in treated cattle. When testing study-level characteristics, season (P = 0.02) and study location (P = 0.02) influenced overall BRD incidence. Metaphylactic programs (lnOR = 0.17; P = 0.05) and technological diagnostic tools (lnOR = 0.40; P = 0.06) modestly decreased overall BRD incidence. Metaphylactic experiments evaluating antimicrobial resistance reduced BRD incidence (lnOR = 1.28; P = 0.01), specifically studies including tulathromycin. Nutritional experiments testing additional vitamin E (lnOR = -0.32; P = 0.05) and pelleting feed (lnOR = 0.34; P = 0.08) had the greatest influence on BRD. The Egger's regression test for funnel plot asymmetry was performed which revealed significant asymmetry (P < 0.0001) suggesting evidence of publication bias. To conclude, BRD tended to decrease in cattle that were applied with treatments, but there was great variation among studies, therefore, the magnitude varied. The results support prioritizing management decisions based on environmental and regional conditions. Interventions for BRD in this analysis suggest that metaphylactic programs and technological diagnostics may be more effective in certain contexts.