Assessing the Effects of Medium Chain Fatty Acids and Fat Sources on Pedv RNA Stability and Infectivity

Research has confirmed that chemical treatments, such as combinations of medium chain fatty acids (MCFA) and commercial formaldehyde, can be effective to reduce the risk of porcine epidemic diarrhea virus (PEDV) cross-contamination in feed. However, the efficacy of individual MCFA levels is unknown. The objective of this study was to compare the efficacy of commercially-available sources of MCFA and other fat sources versus a synthetic custom blend of MCFA to minimize the risk of PEDV cross-contamination as measured by qRT-PCR and bioassay. Treatments were arranged in a 17×4 plus 1 factorial with 17 treatments: 1) Positive control with PEDV and no chemical treatment, 2) 0.3% commercial formaldehyde (Sal CURB, Kemin Industries, Des Moines, IA), 3) 1% MCFA blend [caproic, caprylic, and capric acids; 1:1:1] (aerosolized), 4) 1% MCFA blend [caproic, caprylic, and capric acids; 1:1:1] (non-aerosolized), 5) 0.66% caproic acid, 6) 0.66% caprylic acid, 7) 0.66% capric acid, 8) 0.66% lauric acid, 9) 1% capric and lauric acid (1:1 ratio), 10) 0.3% FRA C12 (Framelco, Raamsdonksveer, Netherlands), 11-15) 1% choice white grease, soy oil, canola oil, palm kernel oil, and coconut oil, and 16-17) 2% palm kernel oil and coconut oil-; 4 analysis days: 0, 1, 3, and 7 post inoculation; and 1 treatment of PEDV negative, untreated feed. Feed was first treated, then inoculated with PEDV, and stored at room temperature until analyzed by qRT-PCR and swine bioassay. The bioassay was carried out by administering day 1 aliquots of treatments by oral gavage to 10 d old pigs, and collecting fecal swabs every 2 days. The values represent threshold cycle (CT), where a higher CT represents less detectable RNA. All main effects and interactions were significant (P<0.002). The interaction of treatment×day indicated that over time the MCFA treatments, either as a mixture (aerosolized 39.0 CT, and non aerosolized 40.0 CT), or as individual fatty acids (caproic 37.0 CT, caprylic 37.3 CT, and capric 35.3 CT), and Sal CURB (37.3 CT), had less detectable PEDV RNA compared to the control (32.7 CT). These treatments also resulted in negative bioassays. Day also had a significant impact as CT increased from 29.5 to 34.6 from day 0 to 7, respectively. In summary, time, Sal CURB, 1% MCFA, 0.66% caproic, 0.66% caprylic, and 0.66% capric acids all enhance the RNA degradation of PEDV in swine feed.