Determining the impact of commercial feed additives as potential porcine epidemic diarrhea virus mitigation strategies as determined by polymerase chain reaction analysis and bioassay()

Gebhardt, Jordan T; Woodworth, Jason C; Jones, Cassandra K; Tokach, Mike D; Gauger, Philip C; Main, Rodger G; Zhang, Jianqiang; Chen, Qi; DeRouchey, Joel M; Goodband, Robert D; Stark, Charles R; Bergstrom, Jon R; Bai, Jianfa; Dritz, Steve S

Additional compounds that have been explored as potential PEDV mitigants in feed and feed ingredients include EOs (Cochrane et al., 2015) . EOs are plant-derived compounds that have been reported to possess antimicrobial characteristics against a number of pathogens including bacteria, yeasts, and viruses (Reichling et al., 2009) . With specific regard to antiviral capabilities, EOs have shown efficacy against enveloped viruses-primarily those affecting humans-including herpes simplex virus, dengue virus, Newcastle disease virus, severe acute respiratory syndrome (SARS), SARS-associated coronavirus, and Junin virus by likely inhibiting viral replication (Reichling et al., 2009) . With specific regard to PEDV, there is little investigation as to the antiviral properties of various EO compounds. Cochrane et al. (2015) evaluated a 2% EO blend consisting of equal ratios of garlic oleoresin, turmeric oleoresin, capsicum oleoresin, rosemary extract, and wild oregano EOs, and observed the greatest reduction of quantifiable genetic material occurred approximately d 14 and beyond in both complete swine diet and spray-dried blood meal. Little impact was observed in spray-dried animal plasma. In the study herein, the combination of EO and BA had the greatest reduction in quantifiable genetic material late in the study period, similar to observations by Cochrane et al. (2015) , suggesting efficacy at reducing quantifiable RNA is not immediate. However, the use of EO alone did not result in a significant reduction in PEDV RNA. Although a dramatic increase in Ct is observed at d 21 and 42 post-laboratory inoculation, it is important to note that the infectivity of the PEDV is lost within complete swine feed by 1 d post-laboratory inoculation and between 7 and 14 d post-laboratory inoculation in SDPP. Thus, although the synergistic effect when combining a BA and EO product is interesting and worthy of investigation, viability of the virus is reduced beyond the point of infectious capability long before such effect on RNA is observed. Similar to Cochrane et al. (2015) , commercial products did not result in a significant increase in Ct in SDPP.