Antimicrobial Drug Consumption on Swiss Pig Farms: A Comparison of Swiss and European Defined Daily and Course Doses in the Field

Complex interplay between PRRSV-1 genetic diversity, coinfections and antimicrobial use influences performance parameters in post-weaning pigs

Porcine reproductive and respiratory syndrome (PRRS) is one of the main diseases of pigs, leading to large economic losses in swine production worldwide. PRRSV high mutation rate and low cross-protection between strains make PRRS control challenging. Through a semi-longitudinal approach, we analysed the relationships among performance parameters, PRRSV-1 genetic diversity, coinfections and antimicrobial use (AMU) in pig nurseries. We collected data over the course of five years in five PRRS-positive nurseries belonging to an Italian multisite operation, for a total of 86 batches and over 200,000 weaners involved. The farm experienced a severe PRRS outbreak in the farrowing unit at the onset of the study, but despite adopting vaccination of all sows, batch-level losses in nurseries in the following years remained constantly high (mean±SE: 11.3 ± 0.5 %). Consistently with previous studies, our phylogenetic analysis of ORF 7 sequences highlighted the peculiarity of strains circulating in Italy. Greater genetic distances between the strain circulating in a weaners' batch and strains from the farrowing unit and the previous batch were associated with increased mortality (p < 0.0001). All the respiratory and enteric coinfections contributed to an increase in losses (all p < 0.026), with secondary infections by Streptococcus suis and enteric bacteria also inducing an increase in AMU (both p < 0.041). Our findings highlight that relying solely on sows' vaccination is insufficient to contain PRRS losses, and the implementation of rigorous biosecurity measures is pivotal to limit PRRSV circulation among pig flows and consequently minimise the risk of exposure to genetically diverse strains that would increase production costs.

The comparison and use of tools for quantification of antimicrobial use in Indonesian broiler farms

Introduction

Indonesia has a large broiler industry with extensive antimicrobial use (AMU) according to empirical evidence. However, there are no quantitative data of on-farm AMU. Quantification of AMU at farm level is crucial to guide interventions on antimicrobial stewardship (AMS). The objective of this study was to compare on-farm AMU monitoring methods, to assess which monitoring method is best suited to gain insight in the quantitative AMU at farm level in medium-scale Indonesian broiler farms.

Method

AMU was calculated using four different indicators—mg/PCU (mass-based), TFUDDindo (Treatment Frequency of Used Daily Dose, dose-based), TFDDDvet (Treatment Frequency of Defined Daily Dose, dose-based), and TFcount − based (count-based)—for the total AMU of 98 production cycles with an average length of 30 days.

Results

Broilers were exposed to an average of 10 days of antimicrobial treatments per production cycle, whereas 60.8% of the antimicrobials belonged to the Highest Priority Critically Important Antimicrobials (HPCIAs). For each pair of indicators, the Spearman rank correlation coefficient was calculated to assess if the production cycles were ranked consistently in increasing AMU across the different indicators. The correlation varied between 0.4 and 0.8.

Discussion

This study illustrates the considerable difference in the ranking of AMU between the different indicators. In a setting comparable to medium-scale broiler farms in Indonesia, where resources are scarce and there is no professional oversight, the TFcount − based method is best suitable. Before implementing an AMU monitoring method, careful consideration of the use-indicators is paramount to achieve fair benchmarking.

Optimizing antimicrobial use by improving medication adherence among pig producers

In Japan, many pig producers buy antimicrobials using veterinarians' prescriptions. Even if veterinarians prescribe antimicrobials for treatments and metaphylaxis, producers may be using them for prophylaxis on farms with a high incidence of chronic diseases. To reduce the frequency of antimicrobial use, we applied the concept of medication adherence and launched an intervention in eight farrow-to-finish farms. For the intervention farms, we attempted to implement measures for preventing the repeated onset of chronic infections that interfered with adherence, confirmed the need to continue medications, and discontinued medications if possible. For each farm, these interventions began at different time points after 2017 and continued until 2020. We evaluated the effectiveness of this intervention based on the amount of active ingredients/population correction unit and the total number of defined daily doses for the weight group/slaughter pig. The ratio of antimicrobial use for both indicators in the year 2020 compared with the start of the intervention decreased on all farms. Among the eight non-intervention farms, six showed an increase in both indicators. These results suggest that interventions for chronic diseases administered by producers and veterinarians lead to high adherence to prescriptions and responsible and prudent use of antimicrobials on pig farms.

In vitro Dissolution Testing and Pharmacokinetic Studies of Silymarin Solid Dispersion After Oral Administration to Healthy Pigs

We evaluated the pharmacokinetics of silymarin solid dispersion in pigs to determine whether silybin bioavailability would be increased over that of a silymarin premix. In vitro dissolution testing was conducted using dissolution apparatus 1 (baskets) at 100 rpm at 37 ± 0.5°C in pH 1.2 HCl, pH 6.8 phosphate, and pH 4.3 acetate buffers containing 0.5% Tween-80. In vivo pharmacokinetics were studied using 16 healthy pigs (Yorkshire × Landrace) that were randomly assigned to two groups. Silymarin as solid dispersion and premix dosage forms were administered directly by stomach tubes at 50 mg kg⁻¹ silybin. In vitro dissolution of silybin for the premix was 35.02, 35.90, and 38.70% in these buffers, respectively. In contrast, silybin dissolution in solid dispersions was increased to 82.92, 87.48, and 99.70%, respectively. Silymarin solid dispersion administered at a single dose resulted in a peak concentration (C_max) of 1,190.02 ± 246.97 ng ml⁻¹ with the area under the curve (AUC_0−∞) at 1,299.19 ± 67.61 ng ml⁻¹ h. These parameters for the premix groups were 411.35 ± 84.92 ng ml⁻¹ and 586.82 ± 180.99 ng ml⁻¹ h, respectively. The C_max and AUC_0−∞ values for the solid dispersion were about twice that of the premix and were consistent with the in vitro dissolution data.

Antimicrobial use on 74 Japanese pig farms in 2019: A comparison of Japanese and European defined daily doses in the field

Defined daily doses (DDD) have been established in human medicine to standardize the measurement of treatment in a population. In veterinary medicine, the European Medicine Agency published defined daily dose (DDDvet) values for antimicrobial agents used in food-producing animals in 2016. National defined doses (DDDjp) for antimicrobials used for pigs in Japan have recently been determined. The aim of this study was to compare the results of calculated antimicrobial use in the field using the DDDjp and DDDvet values. Data from 74 pig farms in Japan relative to antimicrobial use in 2019 was collected. The numbers of DDDs (the weight of biomass treated in kg-days) using DDDjp and DDDvet values for each farm and for different antimicrobial classes were compared. Associations between calculated numbers of DDDjp and DDDvet on farm level were investigated. In addition, differences in antimicrobial use were investigated between different production types of farms (farrowing, finishing and farrow-to-finish farms). Using DDDjp and DDDvet values, the aggregated number of DDDs for 74 farms were 4,099,188 and 2,217,085 respectively, with the former being larger by 1.85 times than the latter. The most frequently used antimicrobial class was penicillin regardless of whether DDDjp or DDDvet was used. The absence of DDDvet values for certain antimicrobial agents used in Japan and the differences in the number of DDDjps/PCU and DDDvets/PCU indicated the need for Japanese DDDs. The number of DDDs per kg population correction unit (PCU) per farm tended to be higher in farrowing farms than in farrow-to-finish farms and finishing farms, with no significant difference (P = 0.19).

Comparison of Antimicrobial Treatment Incidence Quantification Based on Detailed Field Data on Animal Level with the Standardized Methodology of the European Medicines Agency in Veal Calves, Switzerland, 2016-2018

Precise quantification of antimicrobial treatment incidence (TI) is crucial for benchmarking. Two widespread methods for treatment incidence quantification were compared for agreement. Field data were obtained from 38 veal farms from 2016 to 2018 (1905 calves, 1864 treatments). Calculation of TI_swiss for calves was based on detailed treatment records using pharmacokinetic values from the Swiss Veterinary Medicines Compendium. The method published by the European Medicines Agency was used to calculate TI in defined daily doses (TI_DDD). For each calf and treatment, TI_swiss and TI_DDD were calculated on level of the antimicrobial class, drug, application route, and farm. The quotient (Q) of TI_swiss and TI_DDD was calculated. Divergence in results between the two methods of ≤25% was arbitrarily set as good agreement. The agreement between TI_swiss and TI_DDD was mostly good. On class level, good agreement was observed for treatments representing 71.5% of the TI_DDD, and 74.5% of the total TI_DDD on drug level. Poor agreement was mainly observed for tylosin and sulfadimidine. The agreement was better for parenteral than for oral treatments (81.6% vs. 72.3%). For practically orientated calculation on farm level, good agreement was observed (77.5% of the TI_DDD). The TI_DDD method showed mostly good agreement, especially for parenteral treatments.

Establishing defined daily doses (DDDs) for antimicrobial agents used in pigs, cattle and poultry in Japan and comparing them with European DDD values

Monitoring of antimicrobial use is essential in the management of the development and selection of antimicrobial resistance. A variety of indicators has become available to monitor antimicrobial use in human and animal medicine. One of them is an indicator based on defined daily dose (DDD). By using the number of DDDs administered and normalising it by the population at risk of being treated over a defined period, one can estimate the number of treatment days with antimicrobial agents in a population. For veterinary medicine, the European Medicines Agency (EMA) has published the European values of DDD (DDDvet) for food-producing animals. In this study, we defined Japanese defined daily doses for antimicrobial agents (DDDjp) using DDD values that we previously assigned for antimicrobial products approved for use in pigs, cattle and poultry in Japan and compared them with DDDvet values. For the comparison, the quotient of Japanese and European values (QDDD) was calculated and the effect of the administration route and the number of active substances contained in the preparation was investigated. A total of 59 DDDjp values were defined for 43 antimicrobial agents using the data of 276 products approved for use in pigs. Likewise, a total of 55 DDDjp values were defined for 32 antimicrobial agents using the data of 196 products for use in cattle, and a total of 27 DDDjps values were defined for 25 antimicrobial agents using the data of 131 products approved for use in poultry. A comparison was made for 42, 28 and 17 pairs of DDDjp and DDDvet values for antimicrobial agents used for pigs, cattle and poultry respectively. The comparison showed median QDDD value of 0.61 and 0.66 for antimicrobial agents used for pigs and cattle respectively (p<0.01), indicating that the Japanese daily doses are significantly lower than the corresponding EMA values in these species. For the antimicrobial agents used for poultry, no significant difference was observed between DDDjp and DDDvet values with a median QDDD value of 1.15. The difference between DDDvet and DDDjp values and absence of DDDvet values for some antimicrobial agents marketed in Japan indicate that DDDjp rather than DDDvet should be used as the basis for the calculation of antimicrobial use monitoring in farm animals in Japan.

Estimating antimicrobial usage based on sales to beef and dairy farms from UK veterinary practices

BACKGROUND

Accurate estimation of antimicrobial use (AMU) is important in assessing reduction of agricultural AMU. This cross-sectional study aimed to evaluate several approaches for estimating AMU at the herd level and to report on AMU for beef and dairy farms in Scotland.

METHODS

Pharmaceutical sales data for 75 cattle herds (2011-2015) were screened for antimicrobial products and aggregated by herd and year. Several denominators for usage estimates were calculated and compared for their suitability at the herd level.

RESULTS

The median total mass of active ingredient sold per kg of bovine livestock was 9.5 mg/kg for beef herds and 14.3 mg/kg for dairy herds. The 'highest priority critically important' antimicrobials (HPCIA) were by total mass of active ingredient, 10.6% of all sales; by total defined daily dose veterinary (DDDVet), 29.8% and by DCDvet, 20.0%. These are the first estimates of AMU for beef cattle in the UK, and for cattle of any kind in Scotland. Estimates of herd-level usage based on population correction unit (PCU) were sensitive to low values for PCU for specific herd-years due to their demographic composition.

CONCLUSION

Pharmaceutical sales data can provide useful estimates of AMU, but estimating usage per PCU is not appropriate for comparing groups of cattle with different demographic compositions or for setting herd-level targets. Total mass of active ingredient per kilogram of livestock is more stable and hence suitable than PCU-based methods for assessing AMU at the herd level.

Indications and patterns of antimicrobial use in pig farms in the southern Kyushu, Japan: large amounts of tetracyclines used to treat respiratory disease in post-weaning and fattening pigs

In Japan, reducing the use of antimicrobials in pig production is a significant issue. However, there are no published reports concerning porcine disease treatment, as related to the age of the pigs and the indications (e.g., organ system) in Japan. In this study, we analyzed the prescription records of 17 farrow-to-finish farms from 2014 to 2018 in southern Kyushu, Japan. The farms’ antimicrobial usage was calculated as the active ingredient per population correction unit (PCU) or the number of treated pigs per PCU using the defined daily dose. All data were analyzed according to the indications and production stages (sows, suckling pigs, post-weaning pigs, and fattening pigs). In terms of active ingredients/PCU, tetracyclines were the most commonly used (43.2–59.3%), and the largest amounts of antimicrobials administered through feeds were for treating the respiratory organs of fattening pigs. In terms of the number of treated pigs/PCU, tetracyclines were most frequently used (16.3–31.1%), and a high frequency of antimicrobials administered through feeds was used for the treatment of respiratory organs in post-weaning pigs. In this study, it was confirmed that tetracyclines were used frequently as a herd treatment for respiratory diseases in post-weaning and fattening pigs in southern Kyushu, Japan. The findings suggest that it is necessary to improve the treatment and prevention of respiratory diseases in post-weaning and fattening pigs in order to reduce the frequencies of antimicrobial treatments.

Antimicrobial Usage Among Different Age Categories and Herd Sizes in Swiss Farrow-to-Finish Farms

In the Swiss pig sector, the usage of antimicrobials has been recorded, evaluated and systematically reduced on a voluntary basis since 2015. This monitoring has been carried out using various methods thereby enabling continuous national scrutiny as well as international comparisons. To gain a better understanding of the dynamics of the antimicrobial usage on Swiss farms, consumption data of farrow-to-finish farms were analyzed for (i) the within-herd relationships among different age categories and (ii) the influence of the herd size. The data were collected on 71 farms for the year 2017, encompassing the amount of active ingredients and number of defined daily doses Switzerland (nDDDch) in total, and stratified for the different age categories of piglets, weaners, fattening pigs, and sows. The differences in nDDDch per animal among the age categories were determined by a Wilcoxon test and subsequent post-hoc analysis according to Bonferroni. The within-herd relationship among the individual age categories as well as the influence of the herd size on nDDDch per animal measured as kept sows were analyzed by simple linear regression. The evaluation of the treatment days showed that 50% of the nDDDch were used in piglets, 44% for weaners, and 3% each for fattening pigs and sows. Compared to the other age categories, the examination of the number of nDDDch per animal showed a significantly higher number for sows, whereas for fattening pigs the number was significantly lower (P < 0.01). The farm-based analysis using linear regression showed a relationship between antimicrobial usage in sows and piglets (P < 0.001; adj. R² = 0.19). Similarly, a significant relationship between larger herd size and increased antimicrobial usage was observed (P = 0.02; adj. R² = 0.06). The present study provides an insight into the antimicrobial treatment dynamics of farrow-to-finish farms. In particular, the age categories piglets and sows—with their higher number of treatment days in total or per animal—are of interest regarding the potential reduction in antimicrobial usage. Likewise, larger farms with higher management requirements were found to be of particular importance for the reduction of antimicrobial usage. Monitoring programs should therefore evaluate different age categories separately to identify problems for individual farms.

Antimicrobial consumption: Comparison of three different data collection methods

The increasing incidence of antimicrobial resistance represents a global threat. As a result, surveillance programmes monitoring antimicrobial consumption and resistance in animals have been implemented in several countries throughout the world. However, such programmes depend on the accurate and detailed collection of data on antimicrobial consumption. For this reason, the aim of this longitudinal study was to compare the consistency of data on antimicrobial consumption between three different data collection methods. Antimicrobial consumption data associated to udder health were collected from 20 veterinary practices and 92 dairy farms for 18 months. The compared data sources were: 1) data extracted from veterinary practice software 2) farm treatment journals and 3) on-farm discarded drug packages (garbage). Two different procedures were chosen to analyse the data issued from treatment journals: 1) only complete entries were analysed 2) entries with missing dosage were supplemented with the information provided by the Swiss Compendium of Veterinary Medicinal Products. The antimicrobial data were divided into intramammary preparations used during lactation (IMM), intramammary preparations used for dry off (DRY) and systemic treatments (SYS). We compared the quantities of injectors (IMM and DRY), the quantities of active substances (SYS) and the treatment incidences (TI) for the defined daily dose (DDD) per 1000 cow-days (IMM and SYS) and the defined course dose (DCD) per 1000 cow-days (DRY). Additionally, the variety of antimicrobial products among the different data sources was compared. The highest quantity of antimicrobials for IMM, DRY and SYS could be collected with the software data. The lowest quantity was collected by using the data of the treatment journal with only complete entries. For IMM and DRY, software and garbage performed similar, with agreement on the number of injectors used in 56.1% of the analysed cases. The widest variety of intramammary antimicrobial preparations was found in the garbage whilst most systemic preparations were collected using software data. The results of the study show a lack of data consistency between the three different data sources. None of the methods was able to collect the integral antimicrobial consumption in the participating farms. Finally, the results emphasise the need to implement a standardised system to quantify and assess the antimicrobial consumption at veterinary practice and farm level.

Does the Use of Different Indicators to Benchmark Antimicrobial Use Affect Farm Ranking?

The need to reduce antimicrobial use (AMU) in livestock production has led to the establishment of national AMU data collection systems in several countries. However, there is currently no consensus on which AMU indicator should be used and many of the systems have defined their own indicators. This study sought to explore the effect of using different internationally recognized indicators on AMU data collected from Irish pig farms and to determine if they influenced the ranking of farms in a benchmarking system. AMU data for 2016 was collected from 67 pig farms (c. 35% of Irish pig production). Benchmarks were defined using seven AMU indicators: two based on weight of active ingredient; four based on the defined daily doses (DDD) used by the European Medicines Agency and the national monitoring systems of Denmark and the Netherlands; and one based on the treatment incidence (TI200) used in several published studies. An arbitrary “action zone,” characterized by farms above an acceptable level of AMU, was set to the upper quartile (i.e., the top 25% of users, n = 17). Each pair of indicators was compared by calculating the Spearman rank correlation and assessing if farms above the threshold for one indicator were also above it for the comparison indicator. The action zone was broadly conserved across all indicators; even when using weight-based indicators. The lowest correlation between indicators was 0.94. Fifteen farms were above the action threshold for at least 6 of the 7 indicators while 10 farms were above the threshold for all indicators. However, there were important differences noted for individual farms between most pairs of indicators. The biggest discrepancies were seen when comparing the TI200 to the weight-based indicators and the TI200 to the DDDA_NED (as used by Dutch AMU monitoring system). Indicators using the same numerator were the most similar. All indicators used in this study identified the majority of high users. However, the discrepancies noted highlight the fact that different methods of measuring AMU can affect a benchmarking system. Therefore, careful consideration should be given to the limitations of any indicator chosen for use in an AMU monitoring system.

Quantification, description and international comparison of antimicrobial use on Irish pig farms

Background

There is concern that the use of antimicrobials in livestock production has a role in the emergence and dissemination of antimicrobial resistance in animals and humans. Consequently, there are increasing efforts to reduce antimicrobial use (AMU) in agriculture. As the largest consumer of veterinary antimicrobials in several countries, the pig sector is a particular focus of these efforts. Data on AMU in pig production in Ireland are lacking. This study aimed to quantify AMU on Irish pig farms, to identify the major patterns of use employed and to compare the results obtained to those from other published reports and studies.

Results

Antimicrobial use data for 2016 was collected from 67 Irish pig farms which represented c. 35% of national production. The combined sample population consumed 14.5 t of antimicrobial by weight of active ingredient suggesting that the pig sector accounted for approximately 40% of veterinary AMU in Ireland in 2016. At farm level, median AMU measured in milligram per population correction unit (mg/PCU) was 93.9 (range: 1.0–1196.0). When measured in terms of treatment incidence (TI200), median AMU was 15.4 (range: 0.2–169.2). Oral treatments accounted for 97.5% of all AMU by weight of active ingredient and were primarily administered via medicated feed to pigs in the post weaning stages of production. AMU in Irish pig production in 2016 was higher than results obtained from the national reports of Sweden, Denmark, the Netherlands and France but lower than the United Kingdom.

Conclusions

Pig production in Ireland is an important consumer of veterinary antimicrobials. The quantities and patterns of AMU on Irish pig farms are comparable to pig production in other European countries but higher than some countries with more advanced AMU reduction strategies. This AMU is characterised by a high proportion of prophylactic use and is primarily administered to pigs post weaning via medicated feed. Further studies to better understand the reasons for AMU on Irish pig farms and strategies to improve health among weaner pigs will be of benefit in the effort to reduce AMU.

Agreement of Benchmarking High Antimicrobial Usage Farms Based on Either Animal Treatment Index or Number of National Defined Daily Doses

Introduction: While treatment frequency as an indicator of antimicrobial consumption is often assessed using defined doses, it can also be calculated directly as an Animal Treatment Index (ATI). In this study, the correlation of calculating antimicrobial usage on Swiss pig farms using either national Defined Daily Doses (DDDch) or an ATI (number of treatments per animal per year) and the agreement between the different methods for the identification of high usage farms were investigated.

Material and Methods: The antimicrobial consumption of 893 Swiss pig herds was calculated separately for suckling piglets, weaned piglets, fattening pigs, lactating and gestating sows using the indicators nDDDch (number of DDDch) per animal per year and ATI. Correlations between the indicators were investigated by calculating Spearman's Rho coefficients. The 5, 10, and 25% highest usage farms were determined by applying both methods and the interrater reliability was described using Cohen's Kappa coefficients and visualized by Bland-Altman plots.

Results: The Spearman's Rho coefficients showed strong correlations (r > 0.5) between nDDDch/animal/year and ATI. The lowest coefficient was shown for the correlation of both indicators in gestating sows (r = 0.657) and the highest in weaned piglets (r = 0.910). Kappa coefficients identifying high usage farms were the highest in weaned piglets (k = 0.71, 0.85, and 0.91, respectively for 5, 10, and 25% most frequent users) and the lowest in gestating sows (k = 0.54, 0.58, and 0.55 for 5, 10, and 25% most frequent users).

Conclusions: In general, the investigated indicators showed strong correlations and a broad agreement in terms of the calculated levels of antimicrobial usage and the identification of high usage farms. Nevertheless, a certain proportion of the farms were defined differently depending on the indicator used. These differences varied by age category and were larger in all age categories except weaned piglets when a higher percentage benchmark was used to define high usage farms. These aspects should be considered when designing scientific studies or monitoring systems and considering which indicator to use.

Small and Large Animal Veterinarian Perceptions of Antimicrobial Use Metrics for Hospital-Based Stewardship in the United States

Background: Robust measurement and tracking of antimicrobial use (AMU) is a fundamental component of stewardship interventions. Feeding back AMU metrics to individual clinicians is a common approach to changing prescribing behavior. Metrics must be meaningful and comprehensible to clinicians. Little is known about how veterinary clinicians working in the United States (US) hospital setting think about AMU metrics for antimicrobial stewardship. Objective: To identify hospital-based veterinary clinicians' attitudes toward audit and feedback of AMU metrics, their perceptions of different AMU metrics, and their response to receiving an individualized prescribing report. Methods: Semi-structured interviews were conducted with veterinarians working at two hospitals in the Eastern US. Interviews elicited perceptions of antimicrobial stewardship in veterinary medicine. Respondents were shown a personalized AMU Report characterizing their prescribing patterns relative to their peers and were asked to respond. Interviews were recorded, transcribed, and analyzed using the framework method with matrices. Results: Semi-structured interviews were conducted with 34 veterinary clinicians (22 small animal and 12 large animal). Respondents generally felt positive about the reports and were interested in seeing how their prescribing compared to that of their peers. Many respondents expressed doubt that the reports accurately captured the complexities of their prescribing decisions and found metrics associated with animal daily doses (ADDs) confusing. Only 13 (38.2%) respondents felt the reports would change how they used antimicrobials. When asked how the impact of the reports could be optimized, respondents recommended providing a more detailed explanation of how the AMU metrics were derived, education prior to report roll-out, guidance on how to interpret the metrics, and development of meaningful benchmarks for goal-setting. Conclusions: These findings provide important insight that can be used to design veterinary-specific AMU metrics as part of a stewardship intervention that are meaningful to clinicians and more likely to promote judicious prescribing.

Impact of the Suissano Health Programme on antimicrobial usage on 291 pig farms in Switzerland

BACKGROUND

In 2015, in Switzerland the Suissano Health Programme was implemented in pig production to improve transparency for antimicrobial usage (AMU) and to reduce the usage of fluoroquinolones (FQ), macrolides and cephalosporins, representing highest priority critically important antimicrobials.

METHODS

In the presented cohort study, the impact of the Suissano programme on the AMU of 291 pig farms between 2016 and 2017 was investigated. AMU was calculated in total numbers of defined course doses (nDCDch) for all farms in the programme. For each single farm the nDCDch/animal/year was determined for four different age categories (suckling piglets, weaned piglets, fattening pigs, sows) as well as each antimicrobial substance separately. Trends between 2016 and 2017 were investigated for all farms as well as the 25 per cent with the highest usage of antimicrobials (high users) separately.

RESULTS

Total AMU measured in nDCDch declined by 23 per cent between 2016 and 2017, but statistically significant differences could not be observed when comparing the data sets of the individual farms. A significantly reduced usage of FQ could be demonstrated in suckling piglets (P=0.003), weaned piglets (P=0.006) and sows (P=0.008) in 2017 compared with 2016. For high users, a significant reduction of total AMU could be shown in suckling piglets (P=0.02), weaned piglets (P=0.0004) and fattening pigs (P=0.01).

CONCLUSION

This study demonstrated a significant reduction in the usage of FQs in suckling piglets, weaned piglets and sows as well as total AMU in suckling piglets, weaned piglets and fattening pigs on high-usage farms.

Comparison of animal daily doses and days of therapy for antimicrobials in species of veterinary importance

Characterizing antimicrobial use in animal populations is critical for purposes of antimicrobial stewardship. While dose-based metrics such as the animal daily dose (ADD) are typically used for such purposes, duration of therapy is emerging as a critical and more intuitive metric. In theory, the number of ADDs should approximate the number of days of therapy (DOTs), but no studies have examined whether this is the case. The objective of this study was to compare antimicrobial ADDs with antimicrobial DOTs in three populations: canine patients, large animal hospital patients, and dairy herds. In the first two populations, dose-based metrics were calculated using administrative hospital records while duration-based metrics were ascertained from manual chart review of individual animals. In the dairy herds, both metrics were obtained via farmer self-report. We found that the correlation between the number of ADDs and DOTs was poor for hospital patients (Lin correlation coefficients of 0.16 and 0.18 for small and large animals, respectively) and that there were often large differences between the two metrics for all populations, with ADDs most often overestimating the number of DOTs. While the median (IQR) differences between the number of DOTs and ADDs were relatively small (-9.4 (-25.7-(-0.92)), 0.34 (-5.0-4.0), and 0.0 (-18.0-9.0) among canine patients, large animal hospital patients, and dairy herds, respectively), the limits of agreement (-89.4-13.2, -37.7-9.9, and -100.0-53.0, respectively) were likely too large to be acceptable for most investigative purposes. Increased discrepancies between the two metrics were significantly associated with certain animal species (e.g., dogs, small ruminants) and drug classes (e.g., penicillins, cephalosporins, macrolides), decreased animal weight, and increased length of hospital stay. While the number of ADDs can approximate the number of DOTs under certain circumstances, the large limits of agreement between these two measurements suggest that the ADD is generally not a reliable proxy for the duration of therapy.