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

There was a tendency for a feed additive × feed matrix × day interaction (P = 0.094; Table 2 ) in which the combination of EO and BA resulted in a reduction of quantifiable RNA on d 21 and 42 at a greater rate in FEED than in the SDPP matrix. There was a significant (P < 0.001) feed matrix × day interaction in which the Ct value increased over time in FEED, whereas there was very little increase over time observed in SDPP. A tendency for a treatment × feed matrix effect (P = 0.085; Table 3 ) was observed. When further evaluated using means separation, FEED treated with the combination of EO and BA had a greater (P < 0.05) PEDV Ct value than other FEED treatments, and all SDPP treatments had the lower PEDV Ct values compared to FEED treatments (P < 0.05). Sufficient evidence of a feed additive × day interaction was not observed (P = 0.259). All main effects were highly significant, including feed additive, day, and feed matrix (P ≤ 0.001; Tables 2 and 3) . Overall, the combination of EO and BA was most effective at reducing the quantity of genetic material (P < 0.001), regardless of feed matrix or day postinoculation. Overall, a greater quantity of PEDV RNA was detected in SDPP relative to FEED (P < 0.001, Ct = 29.3 ± 0.20 vs. 35.0 ± 0.20, respectively). The main effect of day postinoculation resulted in an increase in PEDV Ct between d 0, 1, 3, 21, and 42 post-laboratory inoculation (P < 0.001; 29.3, 30.7, 31.6, 33.9, and 35.2, respectively). There was no difference in Ct between d 3, 7, and 14 post-laboratory inoculation (P > 0.05, 31.6, 32.1, and 32.2, respectively).