Michael D. Apley

Antimicrobial resistance (AMR) is an increasing concern in food animal production. In swine herds, viral infections often lead to secondary bacterial disease and higher antimicrobial use (AMU). This study describes how U.S. swine veterinarians view the role of viral vaccines in reducing this reliance on antimicrobials. We conducted a national survey of swine practitioners and follow-up semi-structured interviews with a subset of respondents. Across participants, porcine reproductive and respiratory syndrome (PRRS), swine influenza (SIV), and rotaviral enteritis were most often named as viral diseases in urgent need of improved vaccines. These diseases cause substantial economic losses and frequently trigger AMU in commercial herds. Veterinarians reported several recurring challenges with current vaccines, including limited cross-protection against field strains, interference from maternally derived antibodies, and short duration of protection. Despite these limitations, most respondents supported vaccination as a key tool to curb AMU and indicated they would accept higher prices for clearly improved products. These findings reveal both a clear need and specific opportunities for future vaccine development to provide broader and more reliable protection, reduce AMU, and help slow the development of AMR.

Antimicrobial resistance (AMR) is a growing global threat driven by the overuse of antibiotics, especially in livestock. In the swine industry, viral diseases often lead to secondary bacterial infections, which increases the need for widespread antimicrobial use (AMU). This study explores the views of U.S. swine veterinarians on using viral vaccines as a way to reduce reliance on antimicrobials. Through a combination of surveys and interviews, our findings found an urgent need for better vaccines for por-cine reproductive and respiratory syndrome, swine influenza, and rotaviral enteritis. These swine diseases cause major economic losses and are a primary reason for AMU. Veterinarians identified several challenges with existing vaccines, including poor cross-protection against different strains, safety concerns, and issues with cost and availability. Despite these limitations, the study found that veterinarians are willing to invest more in improved vaccines, highlighting a strong demand for more effective tools to reduce antimicrobial use. This research identifies key opportunities for future vaccine development and veterinary strategies to create more effective approaches that protect both animal and public health.

Antimicrobial resistance (AMR) is a significant global health concern, and the use of antibiotics in livestock, including swine production, is a major contributor. Vaccines offer a promising alternative for controlling bacterial infections in pigs, but their widespread use is often hindered by biological, economic, and practical challenges. This study surveyed U.S. swine veterinarians to identify which bacterial diseases require better vaccines and to understand the barriers to their adoption. Nineteen veterinarians with an average of 24.7 years of experience were surveyed across 21 states. The results identified Streptococcus suis, Escherichia coli, Mycoplasma hyopneumoniae, and Glaesserella parasuis as the most critical pathogens needing improved vaccines. Veterinarians anticipated significant improvements in vaccine efficacy for S. suis and E. coli during the nursery stage and expressed a willingness to pay 1.8 and 1.9 times their current prices, respectively. While expectations for M. hyo vaccine improvements were not significant, veterinarians expressed the highest willingness to pay (4.2 times the current price), citing the potential for disease eradication. This research highlights that developing effective vaccines for S. suis and E. coli should be the most urgent priority due to their significant economic impact and rising AMR concerns. However, M. hyo vaccine development holds the most economic potential due to the possibility of eradication. Our research provides a roadmap for future efforts to combat AMR in the swine industry, emphasizing key economic, policy, and educational considerations for successful vaccine implementation.

Antimicrobial resistance (AMR) is a significant global health concern, and the use of antibiotics in livestock, including swine production, is a major contributor. Vaccines offer a promising alternative for controlling bacterial infections in pigs, but their widespread use is often hindered by biological, economic, and practical challenges. This study surveyed U.S. swine veterinarians to identify which bacterial diseases re-quire better vaccines and to understand the barriers to their adoption. Nineteen vet-erinarians with an average of 24.7 years of experience were surveyed across 21 states. The results identified Streptococcus suis, Escherichia coli, Mycoplasma hyopneumoniae, and Glaesserella parasuis as the most critical pathogens needing improved vaccines. Veter-inarians anticipated significant improvements in vaccine efficacy for S. suis and E. coli during the nursery stage and expressed a willingness to pay 1.8 and 1.9 times their current prices, respectively. While expectations for M. hyo vaccine improvements were not significant, veterinarians expressed the highest willingness to pay (4.2 times the current price), citing the potential for disease eradication. This research highlights that developing effective vaccines for S. suis and E. coli should be the most urgent priority due to their significant economic impact and rising AMR concerns. However, M. hyo vaccine development holds the most economic potential due to the possibility of erad-ication. Our research provides a roadmap for future efforts to combat AMR in the swine industry, emphasizing key economic, policy, and educational considerations for successful vaccine implementation.

Humane euthanasia is an endpoint for production animals succumbing to disease or trauma. Euthanasia performed with barbiturates or other anesthetic/sedative drugs observes zero withdrawal time, and drug residues may remain in tissues. Carcasses may be submitted for rendering, and rendered products can be used to manufacture pet foods. The purpose of this study was to determine the concentration of two drugs, xylazine and ketamine, that may be used during the euthanasia process of food animals and to determine the fate of these drugs following a simulated rendering process using a commercial autoclave. Twelve cattle were administered xylazine or xylazine and ketamine prior to euthanasia via penetrating captive bolt, and samples of muscle, fat, liver, and kidney were collected. The tissue samples were analyzed by LC-MS/MS, both raw and following rendering. The parent compounds xylazine and ketamine were detected in all tissues, both before and after rendering. The highest concentrations were found in rendered kidney for both drugs, and the lowest in rendered and raw fat for xylazine and ketamine, respectively.

Field-based diagnostic technologies which aid in the early detection of bovine respiratory disease (BRD) are of great need, given the rising attention related to animal welfare and antimicrobial stewardship. This induced BRD study followed 12 Holstein calves through pre-challenge (day 1–3) and post-challenge (day 6–13) periods with daily sampling of nasal secretions with nasal swabs and expired air with air collection bags for determination of BRD status by use of an electronic nose (eNose). Animals were challenged with bovine herpes virus-1 (BHV-1) on day 3 following sample collection and Mannheimia haemolytica on day 5. Results demonstrated a high degree of accuracy for the eNose in correctly classifying pre-challenge samples for nasal swabs (93.5%) and expired air (96.8%). Post-challenge correct classification by the eNose was 97.8% for nasal swabs and 72.5% for expired air samples. Logistical regression was used to determine the probability of agreement between eNose classification and actual animal BRD status by study day. The largest discrepancy between nasal swab and expired air samples fell on days 6 and 7, immediately following the bacterial challenge. The eNose demonstrated potential as a field-based diagnostic tool for the detection of BRD with nasal swabs as the optimal sample type.

Field-based diagnostic technologies which aid in the early detection of bovine respiratory disease (BRD) are of great need, given the rising attention related to animal welfare and antimicrobial stewardship. This induced BRD study followed 12 Holstein calves through pre-challenge (day 1-3) and post-challenge (day 6-13) periods with daily sampling of na-sal secretions with nasal swabs and expired air with air collection bags for determination of BRD status by use of an electronic nose (eNose). Animals were challenged with bovine herpes virus-1 (BHV-1) on day 3 following sample collection and Mannheimia haemolytica on day 5. Results demonstrated a high degree of accuracy for the eNose in correctly classifying pre-challenge samples for nasal swabs (93.5%) and expired air (96.8%). Post-challenge correct classification by the eNose was 97.8% for nasal swabs and 72.5% for expired air samples. Logistical regression was used to determine the probability of agreement between eNose classification and actual animal BRD status by study day. The largest discrepancy between nasal swab and expired air samples fell on days 6 and 7, immediately following the bacterial challenge. The eNose demonstrated potential as a field-based diagnostic tool for the detection of BRD with nasal swabs as the optimal sample type.

Plasma chlortetracycline (CTC) concentration data were subjected to Monte Carlo simulation of area under the concentration curve (AUC) values related to bovine respiratory disease pathogen MIC distributions to evaluate target attainment rates. Crossbred Hereford heifers were randomly assigned into two treatment groups. Treatment group (A) received chlortetracycline (CTC) at a target dose of 22 mg/kg of bodyweight daily for 5 consecutive days (n = 8) and group (B) received CTC at 350 mg/head per day (1.5 ± 0.2 mg/kg based on actual bodyweights) for seven consecutive days (n = 8). Non‐compartmental analysis was used to calculate plasma‐free drug CTC area under the concentration curves. The mean observed (±SD) free drug AUC values were 4.18 (±1.72) μg × h/mL and 0.30 (±0.06) μg × h/mL for treatment groups A and B, respectively. The probability of target attainment for AUC₂₄/MIC values of 25 and 12.5 was modeled using Monte Carlo simulations. Treatment group A achieved >90% target attainment (AUC₂₄/MIC of 25) at an MIC of 0.06 μg/mL, whereas treatment group B displayed only 12.6% target attainment (AUC₂₄/MIC of 12.5) at the lowest MIC evaluated (0.015 μg/mL). Both in‐feed CTC regimens failed to obtain a reasonable target attainment rate in light of expected MIC distributions of potential pathogens.

The objective of this study was to report antimicrobial use in a convenience sample of U.S. beef feedyards for the years 2018 and 2019. In addition to antimicrobial use metrics, also reported are the indications for antimicrobial use and outcomes related to these indications. Antimicrobial use is characterized at the study and feedyard levels for a total of 1,141,846 head of cattle in 20 U.S. feedyards. Antimicrobial use is reported as milligrams of active antimicrobial ingredient per kilogram of liveweight sold (mg/kg-LW) and regimens of antimicrobials per animal year (Reg/AY). Regimens are described by antimicrobial class within use category as characterized by mg of active antimicrobial product per regimen (mg/Reg) and calendar days of administration per regimen (CDoA/Reg). A total of 1,128,515 regimens of medically important antimicrobials were captured from records. The number of regimens/100 head-in (Reg/100 head-in) are described in a subset of 10 feedyards with adequate data granularity to directly determine indications for antimicrobial administration. For the indications of bovine respiratory disease (BRD), Lameness (Lame), Liver Abscess Control (LAC), and Other (e.g., central nervous system disease, cellulitis) the Reg/100 head-in study-level values are 37.1, 0.8, 98.4, and 0.7, respectively, for 2018, with similar values for 2019. The regimens for BRD are further categorized in these 10 feedyards by the use categories in-feed, control of BRD, and individual animal therapy, yielding study level values of 4.6, 19.6, and 12.9 Reg/100 head-in, respectively, for 2018, with similar values for 2019. Outcomes of therapy for individual animal treatment of BRD, Lame, and Other are reported as treatment success, retreatment, or mortality by 30 days after the initial therapy of an animal for a disease. Treatment success rates (no treatment or mortality in the next 30 days) for 2018 in the 10 feedyards with sufficient data granularity are 76.5, 86.5, and 83.0% for BRD, Lame, and Other, respectively. The comparison of these results with other reports of antimicrobial use in North American feedyards highlights how differing approaches in calculating metric values may result in substantially different conclusions regarding antimicrobial use, especially in relation to long-duration uses.

In order to accurately portray antimicrobial use in food animals, the need for standardized metrics, and an understanding of the characteristics of different metrics, has long been recognized. Fourteen U.S. feedyards were used to evaluate the effects of using centralized constants such as defined daily dose (DDD) and defined course dose (DCD) applied to the weight of medically important antimicrobials by class (mg) as opposed to using electronic individual animal treatment records and lot level in-feed antimicrobial records obtained from the same population. Three numerators were calculated directly from recorded data for each drug product: the number of antimicrobial regimens associated with indication (Reg), milligrams of drug administered per regimen (mg), and calendar days of administration for each regimen (CDoA). There were four use indications to which numerators were assigned: liver abscess control (LAC), bovine respiratory disease (BRD), lameness (lame), or all other indications combined (other). Three denominators were also calculated directly from the data, these being the number of days animals were present (head days), number of cattle received (head in), and kilograms of live weight sold (kg-LW). Numerators and denominators were calculated at the lot level. The use of DDD or DCD was explored to determine how their use would affect interpretation of comparisons between lots or feedyards. At the lot level across both study years, the lot estimate of nDDD differed from the CDoA value by >25% in 49.2% of the lots. The number of Defined Course Doses (nDCD) was then compared to the number of Regimens (Reg). Comparing nDCD to Reg at the lot level across both study years, the lot estimate of nDCD differed from the Reg value by >25% in 46.4% of lots. Both year and metric were also shown to affect numerical feedyard ranking by antimicrobial use according to seven different metrics. The analysis reported here adds to the body of literature reporting substantial effects of metric choice on the conclusions drawn from comparing antimicrobial use across multiple production sites.