Table 2.
Effects of porcine epidemic diarrhea virus (PEDV) dose, pelleting temperature, and conditioning retention time on PEDV detection from feed, pig fecal swabs, and cecum contents, Exp. 11
| PEDV N gene quantitative reverse transcription PCR, cycle threshold (Ct)4 | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Fecal swabs | Cecum contents | ||||||||
| PEDV dose, temperature,2 and time3 | Tissue culture | Feed | 0 dpi5 | 2 dpi | 4 dpi | 6 dpi | 7 dpi | 7 dpi | |
| Unprocessed virus-free feed6 | 45.0 | – | – | – | – | – | – | ||
| Low-dose inoculated feed7 | 20.0 | 30.7e | – | 22.4 | 18.2 | 18.8 | 24.1 | 26.7 | |
| 68.3°C | 45 s | 42.6ab | – | – | – | – | – | – | |
| 90 s | 39.5bcd | – | – | – | – | – | – | ||
| 180 s | 45.0a | – | – | – | – | – | – | ||
| 79.4°C | 45 s | 36.7cd | – | – | – | – | – | – | |
| 90 s | 39.7bc | – | – | – | – | – | – | ||
| 180 s | 42.3ab | – | – | – | – | – | – | ||
| 90.6°C | 45 s | 39.7bc | – | – | – | – | – | – | |
| 90 s | 37.4cd | – | – | – | – | – | – | ||
| 180 s | 35.9d | – | – | – | – | – | – | ||
| High-dose inoculated feed8 | 13.0 | 23.9f | – | 23.0 | 15.3 | 20.4 | 24.3 | 24.0 | |
| 68.3°C | 45 s | 30.2e | – | – | – | – | – | – | |
| 90 s | 29.7e | – | – | – | – | – | – | ||
| 180 s | 30.2e | – | – | – | – | – | – | ||
| 79.4°C | 45 s | 30.1e | – | – | – | – | – | – | |
| 90 s | 29.5e | – | – | – | – | – | – | ||
| 180 s | 30.2e | – | – | – | – | – | – | ||
| 90.6°C | 45 s | 30.1e | – | – | – | – | – | – | |
| 90 s | 30.6e | – | – | – | – | – | – | ||
| 180 s | 30.0e | – | – | – | – | – | – | ||
| SEM | 1.27 | ||||||||
a–fMeans within a column with different superscripts differ (P < 0.05).
1An initial tissue culture containing a low dose and high dose of PEDV was used to inoculate batches of feed. Three feed samples per batch were collected and diluted in PBS. The supernatant from each sample was then collected for pig bioassay. The supernatant was administered 1 time via oral gavage on d 0 to each of 3 pigs per treatment (10 mL per pig). Therefore, each value represents the mean of 3 pigs per treatment. Pigs were initially 10 d old and 3.6 kg BW.
2Temperature of feed exiting the conditioner.
3Retention time: the amount of time required for feed to pass through the conditioner.
4In each instance a (–) signals a negative pig in the bioassay and a (+) represents a positive fecal swab in the bioassay. Each day after inoculation within each treatment has 3 symbols with each row and column, which represents 1 of the 3 pigs in each treatment.
5dpi = days after inoculation.
6A Ct of >45 was considered negative for the presence of PEDV RNA.
7For low-dose feed, PEDV (1 · 103 tissue culture infectious dose [TCID]50(the concentration used to see cytopathic effect in 50% of the cells)/mL) was diluted into feed to provide a dose of 1 · 102 TCID50/g of feed.
8For high-dose feed, PEDV (1 · 105 TCID50/mL) was diluted into feed to provide a dose of 1 · 104 TCID50/g of feed.