Evaluation of animal-to-animal and community contact structures determined by a real-time location system for correlation with and prediction of new bovine respiratory disease diagnoses in beef cattle during the first 28 days after feedlot entry.

OBJECTIVE To determine whether animal-to-animal and community contact patterns were correlated with and predictive for bovine respiratory disease (BRD) in beef steers during the first 28 days after feedlot entry. ANIMALS 70 weaned beef steers (mean weight, 248.9 kg). PROCEDURES Calves were instrumented with a real-time location system transmitter tag and commingled in a single pen. The location of each calf was continuously monitored. Contact between calves was defined as ≤ 0.5 m between pen coordinates, and the duration that 2 calves were within 0.5 m of each other was calculated daily. Bovine respiratory disease was defined as respiratory tract signs and a rectal temperature > 40°C. Locational data were input into a community detection program to determine daily calf contact and community profiles. The number of BRD cases within each community was determined. A random forest algorithm was then applied to the data to determine whether contact measures were predictive of BRD. RESULTS Probability of BRD was positively correlated with the number of seconds a calf spent in contact with calves presumably shedding BRD pathogens and number of calves with BRD within the community on the day being evaluated and the previous 2 days. Diagnostic performance of the random forest algorithm varied, with the positive and negative predictive values generally < 10% and > 90%, respectively. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that direct transmission of BRD pathogens likely occurs among feedlot cattle. The relative contribution of animal-to-animal contact to BRD risk remains unknown and warrants further investigation.

Do antimicrobial mass medications work? A systematic review and meta-analysis of randomised clinical trials investigating antimicrobial prophylaxis or metaphylaxis against naturally occurring bovine respiratory disease.

A distinct difference between veterinary and human medicine is the routine use of antimicrobial mass medications (prophylaxis, metaphylaxis) to healthy individuals. The need for antimicrobial mass medications is based on beliefs that group/s of animals will contract a bacterial disease (i.e. morbidity) and/or die (i.e. mortality). Bovine respiratory disease (BRD) represents the major indication for cattle antimicrobials worldwide. The objectives were to perform a systematic review and meta-analysis of randomised controlled clinical trials (RCTs) for naturally occurring BRD investigating antimicrobial prophylaxis/metaphylaxis to prevent morbidity/mortality. In total, 58 publications met the inclusion criteria summarizing 169 individual RCTs, spanning 50 years (1966-2016). Antimicrobial prophylaxis and metaphylaxis demonstrated moderate, yet highly variable relative risk reductions in BRD morbidity. These were dependent on the antimicrobial classes used, dependent on metaphylaxis definition, BRD attack rates and duration of the RCTs. Best relative risk reductions were from broad-spectrum critically important antimicrobials, or combinations. BRD prophylaxis/metaphylaxis represents major antimicrobial consumption for highly variable short-term gains in absolute risk reduction of morbidity/mortality. Despite widespread use of prevention products, the need for antimicrobial mass medications should be re-evaluated since the underlying problem is more likely the segmented infrastructure of the feedlot and veal calf industries compared to the disease itself.

Bovine Viral Diarrhea Virus-Associated Disease in Feedlot Cattle.

Bovine viral diarrhea virus (BVDv) is associated with bovine respiratory disease complex and other diseases of feedlot cattle. Although occasionally a primary pathogen, BVDv's impact on cattle health is through the immunosuppressive effects of the virus and its synergism with other pathogens. The simple presence or absence of BVDv does not result in consistent health outcomes because BVDv is only one of many risk factors that contribute to disease syndromes. Current interventions have limitations and the optimum strategy for their uses to limit the health, production, and economic costs associated with BVDv have to be carefully considered for optimum cost-effectiveness.

Enfermedades Transmitidas por Alimentos Parte 2

Brucelosis y otras enfermedades transmitidas por alimentos