The effects of group size and subtherapeutic antibiotic alternatives on growth performance and morbidity of nursery pigs: a model for feed additive evaluation

Olsen, Kristin M; Gabler, Nicholas K; Rademacher, Chris J; Schwartz, Kent J; Schweer, Wesley P; Gourley, Gene G; Patience, John F

Indeed, health status has been discussed repeatedly as a potential reason for inconsistencies in response to AGP alternatives (Allen et al., 2013; Boas et al., 2016) . Some studies have shown the potential for AGP alternatives to mitigate a health challenge (Bhandari et al., 2008; Gebru et al., 2010; Heo et al., 2010) ; benefits of AGP alternatives to animal health during a disease challenge would be of great interest to the swine industry. Thus far, the impact of specific AGP alternatives in the presence of particular pathogens is not well understood, and information about health status is mostly absent in published AGP alternative studies (Schweer et al., 2017a) . Documentation of the pathogens present in a group of pigs that may influence the outcome of a study will help to build an understanding of how AGP alternatives may perform under varying health conditions. In this study, the collection of oral fluid and serum samples as well as necropsies of pigs that died allowed for the identification or exclusion of critical pathogens, including PRRSV, as influential factors in this group of pigs. Collection and testing of diagnostic samples, especially at the beginning and end of a study, can be used to assess and document pathogen exposure. If clinical signs of illness are observed, additional samples should be collected, based on the symptoms, to characterize the illness. Major changes in health status throughout a trial should be reported. Table 7 outlines examples of potential pathogens of interest and methods of testing for them.