Antibiotic and medical zinc oxide usage in Danish conventional and welfare-label pig herds in 2016-2018

Towards identification of new genetic determinants for post-weaning diarrhea in piglets

Post-weaning diarrhea in pigs is a considerable challenge in the pig farming industry due to its effect on animal welfare and production costs, as well as the large volume of antibiotics, which are used to treat diarrhea in pigs after weaning. Previous studies have revealed loci on SSC6 and SSC13 associated with susceptibility to specific diarrhea causing pathogens. This study aimed to identify new genetic loci for resistance to diarrhea based on phenotypic data. In depth clinical characterization of diarrhea was performed in 257 pigs belonging to two herds during the first 14 days post weaning. The daily diarrhea assessments were used for the classification of pigs into case and control groups. Pigs were assigned to case and control groups based only on the incidence of diarrhea in the second week of the study in order to differentiate between differences in etiology. Genome-wide association studies and metabolomics association analysis were performed in order to identify new biological determinants for diarrhea susceptibility. With the present work, we revealed a new locus for diarrhea resistance on SSC16. Furthermore, studies of metabolomics in the same pigs revealed one metabolite associated with diarrhea.

Protecting the piglet gut microbiota against ETEC-mediated post-weaning diarrhoea using specific binding proteins

Post-weaning diarrhoea (PWD) in piglets presents a widespread problem in industrial pig production and is often caused by enterotoxigenic E. coli (ETEC) strains. Current solutions, such as antibiotics and medicinal zinc oxide, are unsustainable and are increasingly being prohibited, resulting in a dire need for novel solutions. Thus, in this study, we propose and evaluate a protein-based feed additive, comprising two bivalent heavy chain variable domain (VHH) constructs (VHH-(GGGGS)3-VHH, BL1.2 and BL2.2) as an alternative solution to manage PWD. We demonstrate in vitro that these constructs bind to ETEC toxins and fimbriae, whilst they do no affect bacterial growth rate. Furthermore, in a pig study, we show that oral administration of these constructs after ETEC challenge reduced ETEC proliferation when compared to challenged control piglets (1-2 log10 units difference in gene copies and bacterial count/g faeces across day 2-7) and resulted in week 1 enrichment of three bacterial families (Prevotellaceae (estimate: 1.12 ± 0.25, q = 0.0054), Lactobacillaceae (estimate: 2.86 ± 0.52, q = 0.0012), and Ruminococcaceae (estimate: 0.66 ± 0.18, q = 0.049)) within the gut microbiota that appeared later in challenged control piglets, thus pointing to an earlier transition towards a more mature gut microbiota. These data suggest that such VHH constructs may find utility in industrial pig production as a feed additive for tackling ETEC and reducing the risk of PWD in piglet populations.

Animal board invited review: Improving animal health and welfare in the transition of livestock farming systems: Towards social acceptability and sustainability

The need to integrate more clearly societal expectations on livestock farming has led the authors of this article to consider that livestock farming systems must be redesigned to position health and welfare at the heart of their objectives. This article proposes a vision of the advances in knowledge required at different scales to contribute to this transformation. After defining health and welfare of animals, the article emphasises the need to consider health in a broader perspective, to deepen the question of positive emotional experiences regarding welfare, and raises the question of how to assess these two elements on farms. The positive interactions between health and welfare are presented. Some possible tensions between them are also discussed, in particular when improving welfare by providing a more stimulating and richer environment such as access to outdoor increases the risk of infectious diseases. Jointly improving health and welfare of animals poses a number of questions at various scales, from the animal level to the production chain. At the animal level, the authors highlight the need to explore: the long-term links between better welfare and physiological balance, the role of microbiota, the psycho-neuro-endocrine mechanisms linking positive mental state and health, and the trade-off between the physiological functions of production, reproduction and immunity. At the farm level, in addition to studying the relationships at the group level between welfare, health and production, the paper supports the idea of co-constructing innovative systems with livestock farmers, as well as analysing the cost, acceptability and impact of improved systems on their working conditions and well-being. At the production chain or territory levels, various questions are raised. These include studying the best strategies to improve animal health and welfare while preserving economic viability, the labelling of products and the consumers' willingness to pay, the consequences of heterogeneity in animal traits on the processing of animal products, and the spatial distribution of livestock farming and the organisation of the production and value chain. At the level of the citizen and consumer, one of the challenges is to better inter-relate sanitary and health perspectives on the one hand, and welfare concerns on the other hand. There is also a need to improve citizens' knowledge on livestock farming, and to develop more intense and constructive exchanges between livestock farmers, the livestock industry and citizens. These difficult issues plead for interdisciplinary and transdisciplinary research involving various scientific disciplines and the different stakeholders, including public policy makers through participatory research.

A Virus-like Particle-Based F4 Enterotoxigenic Escherichia coli Vaccine Is Inhibited by Maternally Derived Antibodies in Piglets but Generates Robust Responses in Sows

F4-positive enterotoxigenic Escherichia coli is associated with diarrhea and poor growth outcomes in neonatal and newly weaned piglets and is thus a major economic and welfare burden in the swine industry. Vaccination of sows with F4 fimbriae protects against the neonatal disease via passive transfer of maternal immunity. However, this strategy does not protect against infection post-weaning. Consequently, prevention and treatment methods in weaner pigs heavily rely on the use of antimicrobials. Therefore, in order to reduce antimicrobial consumption, more effective prophylactic alternatives are needed. In this study, we describe the development of a capsid virus-like particle (cVLP)-based vaccine targeting the major F4 fimbriae subunit and adhesion molecule, FaeG, and evaluate its immunogenicity in mice, piglets, and sows. cVLP-display significantly increased systemic and mucosal antibody responses towards the recombinant FaeG antigen in mice models. However, in piglets, the presence of anti-F4 maternally derived antibodies severely inhibited the induction of active humoral responses towards the FaeG antigen. This inhibition could not be overcome, even with the enhanced immunogenicity achieved via cVLP display. However, in sows, intramuscular vaccination with the FaeG.cVLP vaccine was able to generate robust IgG and IgA responses that were comparable with a commercial fimbriae-based vaccine, and which were effectively transferred to piglets via colostrum intake. These results demonstrate that cVLP display has the potential to improve the systemic humoral responses elicited against low-immunogenic antigens in pigs; however, this effect is dependent on the use of antigens, which are not the targets of pre-existing maternal immunity.

Easy and reliable assessment of the prevalence of porcine post-weaning diarrhoea

Post-weaning diarrhoea is a condition of increasing importance due to recent restrictions and bans on the preventive use of antimicrobials and medicinal zinc oxide. For various purposes, it is valuable to monitor the occurrence of post-weaning diarrhoea. The aim of this paper was to propose a protocol for easy and reliable assessment of the prevalence of post-weaning diarrhoea within a section of pigs as an alternative to clinical examination of a random sample of pigs. Two datasets were collected in two different observational field investigations, including more than 4000 individual clinical examinations of newly weaned pigs. First we identified a clinical marker for post-weaning diarrhoea. Second, we drew samples by simulation from our two dataset using different simplified sampling strategies and compared these to conventional random sampling strategies. The prediction error for estimates of the diarrhoea prevalence within a section was compared for the different sampling strategies. The study showed that pigs with diarrhoea had an increased risk of displaying diarrheic soiling of the hind part as well as dull, long, and bristly hair coat, and possibly also hollow flanks and a suboptimal body condition score. Diarrheic soiling of the hind part was the best clinical predictor of diarrhoea; our best estimate of the diagnostic sensitivity was 76.1% (95% credible interval: 72.0, 79.8), and the specificity was 97.1% (95% credible interval: 96.5 0.97.7). Diarrheic soiling of the hind is only a valid clinical predictor of diarrhoea for the first 14 days after insertion into the nursery unit. The precision and accuracy of prevalence estimates were similar for haphazard sampling compared to random sampling of the pigs. Likewise, sampling from a restricted number of pens produced prediction errors similar to sampling across all pens. Yet, the study had limitations regarding sample sizes, and furthermore it is difficult to provide certainty for absence of effects. We recommend sampling pigs haphazardly within at least three randomly selected pens for post-weaning diarrhoea prevalence surveys in order to easily obtain a reliable prevalence estimate. Based on our findings, we conclude the paper by proposing a simple four-step protocol for surveys of the within-section prevalence of post-weaning diarrhoea.

Molecular Characterisation of Antimicrobial Resistance in E. coli Isolates from Piglets in the West Region of Romania

Antibiotics are widely used for prophylaxis and therapy, reducing morbidity and mortality produced by bacterial pathogensin pigs, including infections caused by Escherichia coli. The aim of this study was to characterise antibiotic resistance phenotypes and genotypes in E. coli isolates in pigs in West Romanian grower farms. Differential phenotypic susceptibility profiles and the contribution of resistance genes to phenotypic expression of susceptibility or resistance were evaluated. A total of 76 E. coli isolates were identified and confirmed by the MicroScan Walk Away System. The occurrence of four resistance genes, ampC, blaZ, blaTEM and tetK in strains resistant to 13 antibiotics was assessed. Of the E. coli isolates, 0% showed resistance to meropenem, 3.9% to tigecycline and 10.5% to piperacillin/tazobactam, whereas, in contrast, 100% were resistant to ampicillin and mezlocillin, 76.31% to piperacillin and 59.3% to tetracycline. The prevalence of resistance genes in resistant isolates detected by q-PCR analysis was 97.0% for ampC, 96% for blaZ, 32.9% for blaTEM and 58.8% for tetK. Penetrance (the proportion of individuals carrying a particular variant of a gene that also expresses an associated trait) was 50% for ampC (32% for amoxicillin/clavulanate, 62% for cefazolin, 32% for cefepime, 100% for cefotaxime, 56% for cefuroxime and 99% for ampicillin), 65% for blaZ (32% for amoxicillin/clavulanate and 99% for ampicillin), 51% for blaTEM (81% for piperacillin) and 44% for the tetK gene (83% for tetracycline). The result of phenotypic antibiotic resistance testing may indicate the presence of plasmid-borne resistance, with a diagnostic odds ratio of a positive phenotypic resistance for tetK being 4.52. As a management decision, the maximum penetrance admitted for using a specific antibiotic for E. coli infections in pigs is recommended to be less than 20%.

An observational field study of porcine post-weaning diarrhea: clinical and microbiological findings, and fecal pH-measurements as a potential diagnostic tool

BACKGROUND

Recently, in-feed medicinal zinc has been phased out in pig production in the European Union. This makes updated knowledge about porcine post-weaning diarrhea (PWD) crucial. The objectives of the present study were to investigate (i) the clinical presentation of PWD in pigs housed in Danish herds that did not use medicinal zinc, specifically the prevalence of diarrhea and whether PWD was associated to clinical signs of dehydration or altered body temperature; (ii) which microorganism are associated to PWD; and iii) whether measurements of the fecal pH have a potential to be used diagnostically to differentiate between infectious etiologies in cases of PWD.

RESULTS

The prevalence of diarrhea varied considerably between the outbreaks in the nine studied herds (median = 0.58, range = 0.10; 0.94). In a cross-sectional design (n = 923), diarrhea was associated with reduced rectal temperature and alkaline feces. Diarrhea was also associated with observably reduced skin elasticity, possibly indicating dehydration. In both diarrheic case pigs (n = 87) and control pigs (n = 86), the presence of Brachyspira pilosicoli, Clostridium perfringens, Cryptosporidium spp., Cystoisopora suis, enterotoxigenic Escherichia coli, Lawsonia intracellularis, porcine circovirus types 2 and 3, rotavirus A, B, C, and H, Samonella enterica spp. enterica, and Trichuris suis was described. PWD was associated with high levels of enterotoxigenic E. coli shedding (odds ratio versus no E. coli detection = 4.79 [CI 1.14; 12.62]). Diarrhea was associated with high levels of rotavirus A shedding (odds ratio versus no/low rotavirus A = 3.80 [CI 1.33; 7.97]). The association between microbiological findings in diarrheic pigs and fecal pH was negligible.

CONCLUSIONS

Enterotoxigenic E. coli was confirmed to be a cause of PWD; however, cases of PWD where enterotoxigenic E. coli was not detected in high levels occurred commonly, and this adds to the increasing evidence suggesting that PWD is not necessarily a result of enteric colibacillosis. Rotaviral enteritis might be a differential diagnosis of PWD. pH-measurements cannot be used to differentiate between differential diagnoses for PWD.

Neomycin resistance in clinical Escherichia coli from Danish weaner pigs is associated with recent neomycin use and presence of F4 or F18 fimbriaes

Neomycin is a first-choice antibiotic for treatment of porcine enteritis caused by enterotoxigenic Escherichia coli (ETEC), but little is known about factors influencing resistance to this drug. The aims of this study were to assess antimicrobial resistance and virulence in 325 E. coli isolates obtained in 2020 from various infections in pigs, and to identify factors associated with neomycin resistance development. Susceptibility to 16 antimicrobial agents was determined by broth microdilution, and occurrence of ETEC-associated virulence factors was screened by PCR and hemolysis on blood agar. Univariate and multivariate logistic regression analyses were performed to determine if age group, virulence factors, or antibiotic use (neomycin and other antibiotics) were associated with neomycin resistance. STa, STb, LT, F4, and F18 were detected in 14%, 37%, 26%, 21% and 23% of the isolates, respectively. Resistance was low for antimicrobials of high public health importance (1.5% for cefotaxime, 1% for colistin and no fluoroquinolone resistance) but high for drugs used for treatment of ETEC enteritis (e.g. 20% for neomycin). Isolates with the ETEC pathotype were significantly associated with the weaner age group and intestinal/fecal origin. Multivariate analysis showed that recent neomycin use and presence of F4 or F18 were significantly associated with neomycin resistance amongst isolates from weaners. These results prove an association between neomycin resistance and use at the farm level. Further research is warranted to determine why neomycin resistance was associated with F4 and F18, and whether neomycin use may co-select for virulent strains.

Effects of zinc oxide and condensed tannins on the growth performance and intestinal health of weaned piglets in ETEC-challenged environment

This experiment was conducted to evaluate effects of zine oxide (ZnO) and condensed tannins (CT), independently or in combination, on the growth performance and intestinal health of weaned piglets in enterotoxigenic Escherichia coli (ETEC-K88)-challenged environment. Randomly divided 72 weaned piglets into 4 groups. Dietary treatments included the following: basic diet group (CON), 1,500 mg/kg zinc oxide group (ZnO), 1,000 mg/kg condensed tannins group (CT), and 1,500 mg/kg zinc oxide +1,000 mg/kg condensed tannins group (ZnO + CT). Dietary ZnO supplementation decreased diarrhea rate from 0 to 14 days, 15 to 28 days, and 0 to 28 days (p < 0.05) and no significant on growth performance. The effect of CT on reducing diarrhea rate and diarrhea index was similar to the results of ZnO. Compared with the CON group, ZnO increased the ileum villus height and improved intestinal barrier function by increasing the content of mucin 2 (MUC-2) in jejunum and ileum mucosa and the mRNA expression of zonula occludens-1 (ZO-1) in jejunum (p < 0.05) and the expression of Occludin in duodenum and ileum (p < 0.05). The effects of CT on intestinal barrier function genes were similar to that of ZnO. Moreover, the mRNA expression of cystic fibrosis transmembrane conductance regulator (CFTR) in jejunum and ileum was reduced in ZnO group (p < 0.05). And CT was also capable of alleviating diarrhea by decreasing CFTR expression and promote water reabsorption by increasing AQP3 expression (p < 0.05). In addition, pigs receiving ZnO diet had higher abundance of phylum Bacteroidetes, and genera Prevotella, and lower phylum Firmicutes and genera Lactobacillus in colonic contents. These results indicated that ZnO and CT can alleviate diarrhea and improve intestinal barrier function of weaned pigs in ETEC-challenged environment. In addition, the application of ZnO combined with CT did not show synergistic effects on piglet intestinal health and overall performance. This study provides a theoretical basis for the application of ZnO in weaning piglet production practices, we also explored effects of CT on the growth performance and intestinal health of weaned piglets in ETEC-challenged environment.

Colistin Use in European Livestock: Veterinary Field Data on Trends and Perspectives for Further Reduction

Polymyxin E (colistin) is a medically important active substance both in human and veterinary medicine. Colistin has been used in veterinary medicine since the 1950s. Due to the discovery of the plasmid-borne mcr gene in 2015 and the simultaneously increased importance in human medicine as a last-resort antibiotic, the use of colistin for animals was scrutinised. Though veterinary colistin sales dropped by 76.5% between 2011 to 2020, few studies evaluated real-world data on the use patterns of colistin in different European countries and sectors. A survey among veterinarians revealed that 51.9% did not use or ceased colistin, 33.4% decreased their use, 10.4% stabilised their use, and 2.7% increased use. The most important indications for colistin use were gastrointestinal diseases in pigs followed by septicaemia in poultry. A total of 106 (16.0%) responding veterinarians reported governmental/industry restrictions regarding colistin use, most commonly mentioning "use only after susceptibility testing" (57%). In brief, colistin was perceived as an essential last-resort antibiotic in veterinary medicine for E. coli infections in pigs and poultry, where there is no alternative legal, safe, and efficacious antimicrobial available. To further reduce the need for colistin, synergistic preventive measures, including improved biosecurity, husbandry, and vaccinations, must be employed.

Swine enteric colibacillosis: Current treatment avenues and future directions

Enteric colibacillosis is a common disease in nursing and weanling pigs. It is caused by the colonization of the small intestine by enterotoxigenic strains of Escherichia coli (ETEC) that make use of specific fimbria or pili to adhere to the absorptive epithelial cells of the jejunum and ileum. Once attached, and when both the immunological systems and the gut microbiota are poorly developed, ETEC produce one or more enterotoxins that can have local and, further on, systemic effects. These enterotoxins cause fluid and electrolytes to be secreted into the intestinal lumen of animals, which results in diarrhea, dehydration, and acidosis. From the diversity of control strategies, antibiotics and zinc oxide are the ones that have contributed more significantly to mitigating post-weaning diarrhea (PWD) economic losses. However, concerns about antibiotic resistance determined the restriction on the use of critically important antimicrobials in food-producing animals and the prohibition of their use as growth promoters. As such, it is important now to begin the transition from these preventive/control measures to other, more sustainable, approaches. This review provides a quick synopsis of the currently approved and available therapies for PWD treatment while presenting an overview of novel antimicrobial strategies that are being explored for the control and treatment of this infection, including, prebiotics, probiotics, synbiotics, organic acids, bacteriophages, spray-dried plasma, antibodies, phytogenic substances, antisense oligonucleotides, and aptamers.

Antibiotic Use in European Pig Production: Less Is More

The goal of this study is to describe the current use of antibiotics in the European pig industry based on an extensive literature review. To achieve this, an overview of results from national (n = 15) and multi-country (n = 2) cross-sectional and longitudinal (n = 2) surveys, which describe antimicrobial use in pigs, is presented. Results are further linked to the outcome of the European Surveillance of Veterinary Antimicrobial Consumption (ESVAC) project. Overall, it was found that weaned piglets received the most antibiotics, followed by suckling piglets resulting in over 80% of the treatments being administered to animals before 10 weeks of age. Furthermore, it was observed that antibiotic use (ABU) was significantly associated across age categories, indicating that farms with a high use in piglets also used more antibiotics in their finishers. This may, among other things, be explained by farmers' habits and behavior. However, above all, the studies showed surprisingly large differences in ABU between the countries. These differences may be related to the differences in disease prevalence and/or differences in the level of biosecurity. However, they may also reflect variations in rules and regulations between countries and/or a difference in attitude towards ABU of farmers and veterinarians that are not necessarily linked to the true animal health situation. Furthermore, it was observed that already a substantial proportion of the European pig production is able to successfully raise pigs without any group treatments, indicating that it is possible to rear pigs without systematic use of antibiotics. Based on the ESVAC data, a decline of 43.2% was observed in sales of antibiotics for animals in Europe between 2011 and 2020. To enable efficient antimicrobial quantification and stewardship, 15 European countries have already established systems for herd level monitoring ABU in pigs.

Evidence-Based Recommendations for Herd Health Management of Porcine Post-Weaning Diarrhea

Simple Summary

In this paper, you will find recommendations on how to prevent post-weaning diarrhea in pigs kept in indoor pig herds. The recommendations are based on the scientific knowledge that is currently available. The authors first validated that Danish veterinarians working with pigs demanded such recommendations. Then, we collected papers written by other researchers who had summarized the scientific knowledge on different topics related to post-weaning diarrhea. From the papers, we extracted and synthesized 79 specific recommendations that may help veterinarians and pig producers make good decisions for their pig herd. The paper exemplifies a novel approach to summarizing and transferring science into practice that may be of interest to people that are not involved with pigs and post-weaning diarrhea.

Abstract

Aided by their advising veterinarians, pig producers need to make difficult decisions regarding herd health management strategies. For instance, the preventive use of antimicrobials and medicinal zinc oxide must be substituted with more sustainable preventive approaches to porcine post-weaning diarrhea. Veterinarians and pig producers may find assistance in knowledge based on evidence in this regard; however, the overwhelming scientific literature is not always readily available. The overall aim of this paper is to suggest herd health management decision-support tools that can aid veterinary-assisted decision making in the control of porcine post-weaning diarrhea at a tactical level. The first objective was to validate the need for a herd health management concept, including two decision-support tools. The second objective was to develop evidence-based recommendations that can aid veterinary-assisted decision-making for the herd health management of post-weaning diarrhea. The first objective was investigated by a questionnaire-based study among veterinary pig practitioners in Denmark. For the second objective, we conducted a scientific summary based on scientific review papers identified through a systematic search in three databases. From the papers, we synthesized and extracted 79 specific recommendations. In this paper, we report comprehensive evidence-based recommendations for the herd health management of post-weaning diarrhea.

Stable antibiotic resistance and rapid human adaptation in livestock-associated MRSA

Mobile genetic elements (MGEs) are agents of horizontal gene transfer in bacteria, but can also be vertically inherited by daughter cells. Establishing the dynamics that led to contemporary patterns of MGEs in bacterial genomes is central to predicting the emergence and evolution of novel and resistant pathogens. Methicillin-resistant Staphylococcus aureus (MRSA) clonal-complex (CC) 398 is the dominant MRSA in European livestock and a growing cause of human infections. Previous studies have identified three categories of MGEs whose presence or absence distinguishes livestock-associated CC398 from a closely related and less antibiotic-resistant human-associated population. Here, we fully characterise the evolutionary dynamics of these MGEs using a collection of 1180 CC398 genomes, sampled from livestock and humans, over 27 years. We find that the emergence of livestock-associated CC398 coincided with the acquisition of a Tn916 transposon carrying a tetracycline resistance gene, which has been stably inherited for 57 years. This was followed by the acquisition of a type V SCCmec that carries methicillin, tetracycline, and heavy metal resistance genes, which has been maintained for 35 years, with occasional truncations and replacements with type IV SCCmec. In contrast, a class of prophages that carry a human immune evasion gene cluster and that are largely absent from livestock-associated CC398 have been repeatedly gained and lost in both human- and livestock-associated CC398. These contrasting dynamics mean that when livestock-associated MRSA is transmitted to humans, adaptation to the human host outpaces loss of antibiotic resistance. In addition, the stable inheritance of resistance-associated MGEs suggests that the impact of ongoing reductions in antibiotic and zinc oxide use in European farms on livestock-associated MRSA will be slow to be realised.

Antibiotic-resistant infections are a growing threat to human health. In 2019, these hard-to-treat infections resulted in 4.95 million deaths making them the third leading cause of death that year. Excessive use of antibiotics in humans is likely driving the emergence of drug-resistant bacteria. But there is a concern that use of antibiotics on livestock farms is also contributing. A type of bacteria traced back to livestock is a growing cause of human infections that do not respond to treatment with the antibiotic methicillin in Europe. It is called livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA).

Bacteria can share genes that make them drug resistant or more deadly. These genes are often carried on mobile genetic elements that promote their movement from one bacterial cell to another. The most common type of LA-MRSA in Europe is clonal-complex 398 (CC398). It has two mobile genetic elements carrying antibiotic-resistance genes, but generally lacks a mobile genetic element that helps the bacterium escape the human immune system. Learning more about how LA-MRSA acquired these genetic changes may help scientists develop better strategies to protect the public.

Matuszewska, Murray et al. analyzed the genomes of more than 1,000 samples of CC398 collected from humans, pigs and 13 other animal species in 28 countries over 27 years. They used this data to reconstruct the bacteria’s evolutionary history. Matuszewska, Murray et al. show that two mobile elements containing antibiotic resistance genes in CC398 were gained decades ago. One is more than 50 years old and was likely acquired around the time antibiotic use in livestock became common. While most CC398 in livestock do not have a mobile element that helps LA-MRSA evade the human immune system, they often gain it when they infect humans. This leads to highly drug-resistant human MRSA infections.

The results of this study suggest that LA-MRSA is a serious threat to human health. The resistance of this bacterium has persisted for decades, spreading across different livestock species and different countries. These drug-resistant bacteria in livestock readily infect humans. Current efforts to reduce antibiotic use in farms may take decades to mitigate these risks. Additionally, the ban on zinc-oxide use on livestock in the European Union (coming into force June 2022) may not help reduce LA-MRSA, because the genes conferring resistance to bacteria and zinc treatment are not always linked.

Economic feasibility of interventions targeted at decreasing piglet perinatal and pre-weaning mortality across European countries

BACKGROUND

Piglet perinatal and pre-weaning mortality is a welfare problem causing economic losses in pig production. In this study, the effects of housing and management interventions on the economic result of sow enterprises representing six European countries (Belgium, Denmark, Finland, Germany, The Netherlands and Spain) were tested. Interventions concerned: (1) installing mechanical ventilation, (2) re-designing of the gestation unit, (3) drying and warming newborn piglets, (4) providing enrichment for gestating sows, including high-fiber dietary supplementation and point-source objects, and (5) music provision and backscratching of sows in the farrowing unit. A bio-economic model was used to determine the effects of interventions on economic outcomes during the nursery phase and to calculate a maximum cost of 1%-point reduction in perinatal and pre-weaning mortality, irrespective of the intervention type. Biological parameters were set according to previous observational and experimental studies. Interventions 1-4 were expected to decrease perinatal mortality, defined as stillbirths and deaths occurring within the first 48 h of postnatal life. Intervention 5 was expected to decrease pre-weaning mortality. Interventions increased fixed (1-3) and variable costs (3-5). We hypothesized that housing and management interventions would have a positive economic effect.

RESULTS

Piglet mortality can be decreased in various ways. Interventions concerning ventilation and re-designing of the gestation unit (1 and 2) were the most beneficial in countries with low housing costs and high perinatal mortality. Drying and warming newborn piglets (3) resulted in varying economic results, with the highest increase in profits obtained in a country with low labor costs and high litter size. Interventions providing sows with enrichment and human-animal interaction (4 and 5) were effective across varying conditions. Regardless of intervention type, policies aiming at 1%-point reduction in perinatal and pre-weaning mortality could cost from €0.2 to €0.5 (average €0.4) and from €0.4 to €0.5 (average €0.5) per piglet, respectively, depending on productions conditions.

CONCLUSIONS

To decrease piglet mortality, farmers should consider low input interventions, such as those targeting appropriate behavior. Our results suggest that providing enrichment or increasing human-animal interaction pays off and brings positive economic result even when piglet mortality is marginally reduced.

A Systematic Review on the Link between Animal Welfare and Antimicrobial Use in Captive Animals

Simple Summary

The threat of antimicrobial resistance is a global health concern, and the misuse of medications is often considered a major contributor. Thus, judicious antimicrobial stewardship in captive animal species (i.e., farm, zoo, companion, and laboratory animals) is paramount and should rely on effective strategies for the reduction of antimicrobial use (AMU). Despite the relationship between welfare, health and productivity, the role that animal welfare can play in such a reduction has been poorly investigated, especially with regards to empirical evidence. This systematic review aimed to summarise the available body of research on the link between animal welfare and AMU in captive species. The low number of publications retrieved from the search, with 76% of them published in the last five years, revealed the knowledge gap pertaining this topic. The majority of publications was on farm animals, suggesting a relevance of the topic for this group, with most of the work (82%) looking at the effect of animal welfare on AMU, rather than the opposite. Overall, better animal welfare was found to be associated with lower AMU. Studies were mainly carried out in EU, likely due to its well-known role as being the avant-garde of animal welfare and AMU. Further research is needed to support these findings, especially concerning other captive species beyond farm animals.

Abstract

This systematic review aimed to assess the link between animal welfare and antimicrobial use (AMU) in captive species (i.e., farm, zoo, companion, and laboratory animals) and its effect. Studies empirically examining the effect of welfare on AMU or vice versa were included. Studies in wild animals were excluded. A total of 6610 studies were retrieved from PubMed^® and Web of Science^® in April 2021. Despite finding several papers superficially invoking the link between welfare and AMU, most did not delve into the characteristics of this link, leading to a small number of publications retained (n = 17). The majority (76%) of the publications were published from 2017–2021. Sixteen were on farm animals, and one publication was on laboratory animals. Most of the studies (82%) looked at the effect of animal welfare on AMU. The body of research retained suggests that, in farm animals, better animal welfare often leads to lower AMU, as was hypothesised, and that, generally, poor welfare is associated with higher AMU. Additionally, AMU restrictions in organic systems may prevent animals from receiving treatment when necessary. Limitations of this study include focusing only on empirical research and excluding non-peer reviewed evidence. More research is needed to corroborate these findings, especially on the link between animal welfare and AMU in other captive species.

Linking Animal Welfare and Antibiotic Use in Pig Farming-A Review

Preventative measures, such as biosecurity and vaccinations, are essential but not sufficient to ensure high standards of health in pig production systems. Restrictive, barren housing and many widely used management practices that cause pain and stress predispose high-performance pigs reared in intensive systems to disease. In this context, antibiotics are used as part of the infrastructure that sustains health and high levels of production in pig farms. Antimicrobial resistance (AMR) is a global emergency affecting human and animal health, and the use of antibiotics (AMU) in intensive livestock farming is considered an important risk factor for the emergence and spread of resistant bacteria from animals to humans. Tackling the issue of AMR demands profound changes in AMU, e.g., reducing their use for prophylaxis and ending it for growth promotion. In support of such recommendations, we revise the link between animal welfare and AMU and argue that it is crucial to sustainably reduce AMU while ensuring that pigs can live happy lives. In support of such recommendations, we aimed to revise the link between animal welfare and AMU in pigs by analysing stress factors related to housing and management and their impact on pig welfare. In particular, we reviewed critical management practices that increase stress and, therefore, pigs' susceptibility to disease and reduce the quality of life of pigs. We also reviewed some alternatives that can be adopted in pig farms to improve animal welfare and that go beyond the reduction in stress. By minimising environmental and management stressors, pigs can become more immunocompetent and prepared to overcome pathogenic challenges. This outcome can contribute to reducing AMU and the risk of AMR while simultaneously improving the quality of life of pigs and, ultimately, maintaining the pig industry's social license.

Post-weaning diarrhea in pigs weaned without medicinal zinc: risk factors, pathogen dynamics, and association to growth rate

BACKGROUND

Porcine post-weaning diarrhea (PWD) has reemerged as an important topic in pig production, as common control strategies based on prophylactic use of antimicrobials and zinc oxide have been deemed unsustainable. The objectives of this study were to estimate the cumulative incidence of porcine post-weaning diarrhea with different etiologies in production systems weaning without zinc oxide and prophylactic antimicrobials, to assess risk factors for post-weaning diarrhea, and to estimate the impact of post-weaning diarrhea on growth rate. A cohort study was conducted at two commercial indoor producers weaning without medicinal zinc oxide and prophylactic antimicrobials.

RESULTS

Piglets were included at birth (n = 300) and 272 survived until weaning. After insertion to the nursery units, the piglets were clinically examined every day for 14 days, and rectal swabs were collected and analyzed for enterotoxigenic Escherichia coli (ETEC) and rotavirus A. The cumulative incidences of PWD the first 14 days after insertion to the nursery units were 41.8% (CI 33.6, 50.4) and 51.1% (CI 42.3, 60.0) at the two producers, respectively. We found a low incidence of cases associated to ETEC, and detected a substantial proportion of cases associated to rotavirus. We observed a biphasic pattern in the assumed etiology with rotavirus occurring first, and then a shift towards cases associated to ETEC/non-ETEC hemolytic E. coli. Being offspring of older sows was a protective factor for the development of PWD (Hazard ratio = 0.88 [CI 0.78, 0.99] per unit increase in parity of the dam). Low birth weight reduced the post-weaning growth rate (- 5.2 g/day [CI - 7.5, - 2.9] per 100 g decrease in birthweight) and increased the hazard of developing PWD (Hazard ratio for birthweight below 1100 g: 2.30 [CI 1.41-3.74]). The combined effect of having diarrhea for 2 days or more and receiving antimicrobial treatment was associated with an increased average daily weight gain.

CONCLUSIONS

This study suggests novel insights regarding pathogen dynamics and risk factors for PWD in productions not using prophylactic antimicrobials and medicinal zinc. The findings may have important implications for both antimicrobial usage and prevention strategies.

Risk Factors for Antimicrobial Use on Irish Pig Farms

Simple Summary

Antimicrobial resistance (AMR) is a major threat to public health. There are concerns that antimicrobial use (AMU) in agriculture has a role in the development of AMR. Pigs are one of the main consumers of veterinary antimicrobials and a better understanding of the drivers for AMU in this sector will help in efforts to reduce use. The aim of this study was to investigate the associations between antimicrobial use, farm characteristics, biosecurity, the presence of respiratory disease on the farm and health management practices on Irish pig farms. Farms that manufactured their feed on-site had lower total AMU than farms that purchased their feed from a feed mill. Higher levels of lung abscesses and pericarditis (inflammation of the lining around the heart), both indicators of respiratory disease, were associated with increased AMU. Higher levels of pericarditis were also associated with increased use of critically important antimicrobials. Farms vaccinating against swine influenza also had higher AMU. Farms that administered prophylactic antimicrobial treatments to piglets had higher use of individual treatments and critically important antimicrobials. The results from this study show that prophylaxis and respiratory disease are the main drivers of AMU on Irish pig farms. These findings highlight areas of farm management where interventions may aid in reducing AMU on Irish pig farms.

Abstract

The threat to public health posed by antimicrobial resistance in livestock production means that the pig sector is a particular focus for efforts to reduce antimicrobial use (AMU). This study sought to investigate the risk factors for AMU in Irish pig production. Antimicrobial use data were collected from 52 farrow-to-finish farms. The risk factors investigated were farm characteristics and performance, biosecurity practices, prevalence of pluck lesions at slaughter and serological status for four common respiratory pathogens and vaccination and prophylactic AMU practices. Linear regression models were used for quantitative AMU analysis and risk factors for specific AMU practices were investigated using logistic regression. Farms that milled their own feed had lower total AMU (p < 0.001), whereas higher finisher mortality (p = 0.043) and vaccinating for swine influenza (p < 0.001) increased AMU. Farms with higher prevalence of pericarditis (p = 0.037) and lung abscesses (p = 0.046) used more group treatments. Farms with higher prevalence of liver milk spot lesions (p = 0.018) and farms practising prophylactic AMU in piglets (p = 0.03) had higher numbers of individual treatments. Farms practising prophylactic AMU in piglets (p = 0.002) or sows (p = 0.062) had higher use of cephalosporins and fluoroquinolones. This study identified prophylactic use and respiratory disease as the main drivers for AMU in Irish pig production. These findings highlight areas of farm management where interventions may aid in reducing AMU on Irish pig farms.