The Impact of Antimicrobial Stewardship Training on Calf Producers' Knowledge, Treatment Behaviors and Quantified Antimicrobial Use.

The judicious use of antimicrobials on farms is necessary to mitigate the development of antimicrobial-resistant pathogens that compromise human and animal health. On livestock farms, veterinarians prescribe and dispense antimicrobials, but producers use rapid judgements of disease severity to make routine decisions on the initiation of empirical antimicrobial therapy. Therefore, the knowledge and skills required to accurately diagnose treatable bacterial infections is necessary for optimal antimicrobial stewardship. Veal calves often undergo stressors and environmental exposures that increase calves' risk of bacterial infections, and antimicrobials are sometimes necessary to ensure their health. The objective of this trial was to measure the impact of antimicrobial stewardship training on calf producers' knowledge of antimicrobial stewardship, accuracy of identifying calves for treatment, and quantified antimicrobial use. Eight farms were evenly allocated into either intervention or control groups. Training resulted in both higher scores on assessments and higher sensitivity for detecting cases that required antimicrobial therapy relative to a veterinarian. Importantly, there was a 50% reduction in the antimicrobial dosing rate among intervention farms relative to control farms. Antimicrobial stewardship training among calf producers was effective at changing producers' behaviors and reducing antimicrobial use.

Antimicrobial Use and Resistance in Surplus Dairy Calf Production Systems.

Surplus calves, which consist predominately of male calves born on dairy farms, are an underrecognized source of antimicrobial-resistant (AMR) pathogens. Current production systems for surplus calves have important risk factors for the dissemination of pathogens, including the high degree of commingling during auction and transportation and sometimes inadequate care early in life. These circumstances contribute to an increased risk of respiratory and other infectious diseases, resulting in higher antimicrobial use (AMU) and the development of AMR. Several studies have shown that surplus calves harbor AMR genes and pathogens that are resistant to critically important antimicrobials. This is a potential concern as the resistant pathogens and genes can be shared between animal, human and environmental microbiomes. Although knowledge of AMU and AMR has grown substantially in dairy and beef cattle systems, comparable studies in surplus calves have been mostly neglected in North America. Therefore, the overall goal of this narrative review is to summarize the existing literature regarding AMU and AMR in surplus dairy calf production, highlight the management practices contributing to the increased AMU and the resulting AMR, and discuss potential strategies and barriers for improved antimicrobial stewardship in surplus calf production systems.

Prevalence and Sources of Salmonella Lymph Node Infection in Special-Fed Veal Calves.

ABSTRACT: Peripheral lymph nodes (LNs) have been implicated as potential contaminants of ground beef, yet the source and timing of Salmonella LN infection in cattle is still unclear, limiting targeted intervention. The aim of this study was to leverage the vertical integration of special-fed veal production to identify preharvest environmental exposures, specifically in livestock trailers and harvest facility holding pens where calves spend 30 min to 4 h, that result in Salmonella LN infection. Ten cohorts of 80 to 82 veal calves were followed through the harvest process, and environmental samples were collected in barns, trailers, and holding pens. Mesenteric LNs from 35 calves were collected at harvest, and 25 prefemoral LNs per cohort were pooled. Within the same cohort, for 12 samples for which the serovar of the environmental and calf LN Salmonella isolates matched, the isolates were submitted for whole genome sequencing to determine whether environmental exposure resulted in LN infection. Cohort-level Salmonella mesenteric LN prevalence ranged from 0% (0 of 35 samples) to 80% (28 of 35 samples), and pooled prefemoral LNs were positive for Salmonella in 3 of the 10 cohorts. Salmonella prevalence in samples from barns, livestock trailers, and harvest facility holding pens was 22% (13 of 60 samples), 74% (59 of 80 samples), and 93% (74 of 80 samples), respectively. Some environmental and LN isolates were multidrug resistant. Four instances of Salmonella transmission from trailers and/or holding pens to calf LNs were supported by sequence data. Salmonella serovars Agona, Give, and Muenster were identified in transmission events. One instance of transmission from the livestock trailer, two instances from holding pens, and one instance from either trailer or holding pens were observed. Further research is needed to evaluate the extent of environmental Salmonella transmission in cattle and to determine whether targeted interventions in trailers or holding pens could reduce novel Salmonella LN infection in veal calves before harvest.