Evaluation of the efficacy of two postweaning colibacillosis vaccines in a field herd with PRRS circulation during postweaning stage

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article.Postweaning diarrhea (PWD) and PRRS are two major concerns in swine production, which association has not been consistently explored. In the current scenario of restrictions in the use of antibiotics and ZnO, vaccination is more relevant to control PWD, but PRRS virus circulation may compromise the immune protection conferred by postweaning colibacillosis vaccines. We evaluated the efficacy of two postweaning colibacillosis vaccines (parenteral and oral) in a commercial herd affected by an outbreak of PWD and with PRRS circulation in postweaning. Five groups were studied during the postweaning period: one control (Group 1) and four vaccinated: two with each postweaning colibacillosis vaccine administered alone (Groups 2 and 3) or with sow vaccination against PRRS (Groups 4 and 5). We evaluated the effects on piglet weight, average daily weight gain and in the percentage of piglets with diarrhea, its duration, lethality and mortality. PRRS viremia and anti-PRRS antibodies were evaluated by qPCR and ELISA. Regarding control group, colibacillosis vaccination generally improved most of the measured parameters; but significant improvements were only observed in Groups 4 and 5 (p < 0.05). Moreover, cases of diarrhea occurred at different ages: in Groups 2 and 3 the peak of cases occurred just after ZnO was removed from the feed compared to Group 1, while in Groups 4 and 5 no peak was observed. This suggests that postweaning colibacillosis vaccination may be compromised by the PRRS circulation. In PRRS endemic herds an effective protection against PWD through vaccination may require PRRS vaccination to obtain a better performanceThis research was supported by the Programme for Consolidating and Structuring Competitive Research Groups (GRC2019/04; Xunta de Galicia, Spain) and by a postdoctoral grant to G. Lopez-Lorenzo (Campus de especializacion, Campus Terra, Universidade de Santiago de Compostela)2024-09-01S