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Background: Recently, we found an association between antibiotic treatment and antibiotic resistance in fecal Escherichia coli from rearing pigs during their life. In this study, our aim was to investigate potential risk factors for antibiotic treatment at different production stages of these pigs.Results: In a longitudinal study, antibiotic use was recorded in commercial pig production chains, starting in 29 breeding herds. Information on housing system and management, management of animals and feeding, animal health and performance was surveyed in the herds. In total 55, 57 and 66 variables were evaluated for the production stages suckling, weaning and fattening. In descriptive and univariable analyses seven to eight variables per production stage were associated with antibiotic use. In multivariable analyses, rodent control carried out by a company was associated with an increased risk of antibiotic treatment (odds ratio (OR), 6.86, confidence limits, CL, 1.12 – 41.83, p = 0.023) at suckling. At weaning, production type (farrow-to-finish vs. movement of pigs to another farm after suckling or weaning; OR 0.15, CL 0.02 – 0.89, p = 0.023) was associated with the risk of antibiotic treatment. During the fattening stage, animals were treated more often when the number of weaned piglets per sow and year increased (additional piglet: OR 2.5, CL 0.6 – 29.6, p = 0.0172).Conclusions: Different risk factors were associated with an increased risk of antibiotic treatment in the individual production stages. Therefore, focus on specific measures, especially at suckling and weaning, when most antibiotics are used, is needed. Further research on key factors driving antibiotic use and the causative pathogens that require treatment is necessary in pig production.

Zusammenfassung Ziel des vorliegenden ersten Teils dieser Untersuchung war, unter definierten Bedingungen die Entstehung und weitere Entwicklung akzessorischer Bursen an den Gliedmaßen von Mastschweinen zu erfassen. Material und Methoden: 192 Masthybriden wurden von der Aufzucht bis zur Schlachtung unter konventionellen Haltungsbedingungen untersucht. Wöchentlich wurden die Parameter Allgemeinbefinden, Anzahl, Größe und Lokalisation der akzessorischen Bursen an Gliedmaßen und Sternum sowie Gang und Klauen erfasst. Ergebnisse: Akzessorische Bursen können an bis zu 13 Stellen an den Gliedmaßen bzw. dem Sternum auftreten. Es wurden bereits Ferkel mit akzessorischen Bursen in die Aufzucht eingestallt, die Prävalenz stieg während Aufzucht und Mast an und lag vor der Schlachtung bei 97,8 % der Tiere (Einstallung mit 4 Wochen: 25,5 %; Umstallung in die Mast mit 12 Wochen: 67,6 %). Schwere Tiere wiesen signifikant mehr und größere Bursen auf als gleichaltrige leichtere Tiere. Außerdem nahmen sie größere Futtermengen auf, riefen aber weniger häufig Futter ab. Tiere mit stärkeren Gangbildveränderungen zeigten signifikant mehr und größere Bursen. Am Schlachthof bestand bei 95,6 % der Tiere mindestens eine Klauenveränderung. Das Allgemeinbefinden wurde durch akzessorische Schleimbeutel nicht beeinträchtigt. Schlussfolgerung und klinische Relevanz: Eine Beeinträchtigung des Wohl-befindens hinsichtlich Schmerzempfinden durch akzessorische Bursen wird aufgrund der vorliegenden Ergebnisse und der Funktion als Schutzkissen nicht vermutet. Dennoch entstehen akzessorische Bursen in hoher Prävalenz und Anzahl pro Tier unter Einfluss verschiedener Faktoren erst im Laufe des Lebens und stellen eine Technopathie dar. Aufgrund der Exposition akzessorischer Bursen besteht das Risiko, dass diese sich infolge von Verletzungen zu eröffneten Grad-3-Bursen entwickeln.

The aim of the first part of the present study was to specify risk factors for the development of adventitious bursae on the limbs of weaning and finishing pigs.In total, 192 pigs were examined weekly, recording the following parameters: general condition, number, size and localization of adventitious bursae on the limbs and sternum, gait and claws.Adventitious bursae can occur at 13 positions on the limbs or sternum. These adventitious bursae were already evident when pigs were moved to the nursery. The prevalence of adventitious bursae increased constantly from weaning to slaughter. At the age of 24 weeks, 97.8 % of all investigated pigs displayed adventitious bursae (aged 4 weeks: 25.5 %; aged 12 weeks: 67.6 %). Heavier pigs had significantly more and larger adventitious bursae than lighter pigs of the same age. Furthermore, heavier pigs retrieved feed from the automatic feeder less frequently but ate larger amounts each time. In addition, pigs with poorer gait displayed significantly more adventitious bursae. In 95.6 % of all investigated pigs, claw lesions were evident at slaughter. The general condition was unaffected by adventitious bursae.Referring to the results of the present study and the general function of bursae protecting underlying structure against pressure, there is no indication that adventitious bursae affect the animal welfare in terms of the sensation of pain. Influenced by various factors, adventitious bursae develop with high prevalence and number per animal over the course of the life of pigs and can be described as a technopathy. Because of the exposure of adventitious bursae, there is a risk to become an ulcerated bursa of degree three in relation to injuries.

The purpose of this longitudinal study was to describe the occurrence of antibiotic resistance in faecal Escherichia coli isolated from pigs between birth and slaughter and its association with antibiotic treatment. Four objectives were addressed: comparison of antibiotic resistance in isolates from a) treated vs. non-treated pigs, b) follow-up vs. initial samples of treated and non-treated pigs, c) pigs receiving treatments via different administration routes and d) sows and their piglets. Each comparison addressed the following antibiotic groups used for treatment: beta-lactams, tetracyclines, polymyxins and macrolides, and the susceptibility of E. coli isolates to the respective agents: ampicillin, tetracycline, colistin and azithromycin. Between 2014 and 2016, 406 focal animals from 29 commercial breeding herds were followed from birth to the end of the relevant fattening periods. All antibiotic treatments in these pigs were documented. Faecal samples were collected from the focal pigs once while suckling, once after weaning and three times during fattening, and from their dams once around farrowing. Escherichia coli isolated from these samples was tested for antibiotic susceptibility. In total, 264 animals from 19 breeding herds were treated with an antibiotic at least once during their lifetime. Beta-lactams, tetracyclines and colistin were used most frequently. Piglets were treated individually by injection (n = 108 treatments) or via drench (9); weaners via feed (192) or water (56) and fatteners via feed (30) or injection (15). Resistance to ampicillin and tetracycline in E. coli was already common prior to antibiotic treatment. Resistance proportions were higher for beta-lactam-, tetracycline-, colistin- and macrolide-treated pigs compared to untreated pigs at different sampling periods (p < 0.05; Fisher's exact test). In the logistic analysis, the difference was confirmed for beta-lactam-treated vs. untreated pigs. In E. coli from macrolide-untreated pigs, resistance to azithromycin was more frequent compared to pre-treatment values. Route of application did not affect rates of antibiotic resistance in the logistic analysis even though Fisher's exact test indicated associations for beta-lactams (feed/water vs. injection), tetracyclines (feed/water vs. non-treatment) and macrolides (tulathromycin-injection vs. tylosin in feed). Piglets were more likely to carry an E. coli resistant to ampicillin or azithromycin if their dams did so as well. Our results suggest further research on resistance effects by administration routes is required. Reducing antibiotic resistance in sows might lead to a lower level of beta-lactam or macrolide-resistant E. coli among their progeny. To preserve treatment options for bacterial infections, antibiotic use should be restricted to necessary cases.