Effects of medium chain fatty acids as a mitigation or prevention strategy against porcine epidemic diarrhea virus in swine feed.

: Feed has been shown to be a vector for viral transmission. Four experiments were conducted to: 1) determine if medium chain fatty acids (MCFA) are effective mitigants when applied to feed both pre- and post- porcine epidemic diarrhea virus (PEDV) inoculation measured by quantitative reverse transcription polymerase chain reaction (qRT-PCR), 2) evaluate varying levels and combinations of MCFA measured by qRT-PCR, and 3) evaluate selected treatments in bioassay to determine infectivity. In Exp. 1, treatments were arranged in a 2×2+1 factorial with main effects of treatment (0.3% commercial formaldehyde product (CF), Sal CURB [Kemin Industries, Inc.; Des Moines, IA] or 1% MCFA blend (Blend) of 1:1:1 C6:C8:C10 [PMI, Arden Hills, MN]) and timing of application (pre- or post-inoculation with PEDV); plus a positive control (PC; feed inoculated with PEDV and no treatment). All combinations of treatment and timing decreased detectable PEDV compared to the PC (P < 0.05). Pre-inoculation treatment elicited decreased magnitude of PEDV detection (Ct value) compared to post-inoculation (P = 0.009). Magnitude of PEDV detection was decreased for CF compared to Blend (P < 0.0001). In Exp. 2, pre-inoculation treatments consisted of: 1) PC, 2) 0.3% CF, 3-5) 0.125 to 0.33% C6:0, 6-8) 0.125 to 0.33% C8:0, 9-11) 0.125 to 0.33% C10:0, 12-15) 0.125 to 0.66% C5:0. Treating feed with 0.33% C8:0 resulted in decreased (P < 0.05) PEDV detection compared to all other treatments. Increasing concentration of each individual MCFA decreased PEDV detectability (P < 0.042). In Exp. 3, pre-inoculation treatments consisted of :1) PC, 2) 0.3% CF, 3-7) 0.25 to 1% Blend, 8-10) 0.125% to 0.33% C6:0+C8:0, 11-13) 0.125% to 0.33% C6:0+C10:0, 14-16) 0.125% to 0.33% C8:0+C10:0. Treating feed with CF, 0.5% Blend, 0.75% Blend, 1 % Blend, all levels of C6:0+C8:0, 0.25% C6:0+0.25% C10:0, 0.33% C6:0+0.33% C10:0, 0.25% C8:0+0.25% C10:0, or 0.33% C8:0+0.33% C10:0 elicited decreased detection of PEDV compared to PC (P < 0.05). Increasing concentration of each MCFA combination decreased PEDV detectability (linear, P < 0.012). In Exp. 4, feed was treated pre-inoculation with: 1) no treatment (PC), 2) 0.3% CF, 3) 0.5% Blend, or 4) 0.3% C8:0 and analyzed via qRT-PCR and bioassay. Adding 0.5% Blend or 0.3% C8:0 resulted in decreased PEDV compared to PC and only PC resulted in a positive bioassay. Therefore, MCFA can decrease detection of PEDV in feed. Further, inclusion of lower levels of MCFA than previously evaluated are effective against PEDV.