Flushing feed mill with treated rice hulls reduces PEDV risk

The porcine epidemic diarrhea virus (PEDV) taught swine veterinarians and producers many hard lessons about feed management. Not only can the deadly virus be transported by feed ingredients, PEDV also can contaminate subsequent batches of feed due to carryover on feed-contact surfaces.¹

Although washing and disinfecting is an effective decontamination method, it’s not practical for commercial feed production. So, a team of researchers from Kansas State and Iowa State universities evaluated chemically treated rice hulls as a more practical solution. Rice hulls were chosen due to their abrasiveness, excellent adsorption and relatively low cost, pointed out Jordan Gebhardt, Kansas State University PhD graduate student in swine nutrition.

The rice hulls were treated with 0.325% formaldehyde, 2% medium-chain fatty acids (MCFA), 10% MCFA or left untreated as a control comparison. A PEDV-contaminated batch of feed was mixed in eight laboratory-scale mixers, followed by one of the four flush treatments. Two replicates were conducted per treatment.

For a larger-scale perspective, PEDV-contaminated feed was manufactured through a 50-kg mixer, followed by a 10%-MCFA-treated rice hull flush. Researchers then mixed another batch of feed.

Contaminated feed and flush samples were tested for PEDV presence. Infectivity was tested through 10-day-old pigs.

The researchers presented a poster at the 2017 American Association of Swine Veterinarians’ meeting in Denver showing their results. For the laboratory-scale mixers, half of the untreated rice hull flushes had detectable PEDV, as did one of six formaldehyde-treated rice hull and two of the 2%-MCFA rice hull flushes. No PEDV was found following the 10%-MCFA rice hull flush. For the larger-scale mixer, no PEDV was detected following the flush or in the next batch of feed.

“PEDV-contaminated control feed transferred infection to the pigs, but the feed processed after the chemically treated rice hull flushes did not,” Gebhardt said.

Researchers also looked at the dust resulting from feed mixing. They found that the contaminated control feed produced contaminated dust and that the PEDV was infective. The 10%-MCFA rice hull flush reduced the PEDV load and the related dust was not infective.

The researchers concluded: “Chemically treated rice hull flushes reduced the quantity of detectable PEDV and potential infectivity in feed, and the 10%-MCFA treatment eliminated PEDV infectivity in dust.”

¹ Gebhardt J, et al. Evaluation of the Effects of Flushing Feed Manufacturing Equipment with Chemically Treated Rice Hulls on PEDV Cross Contamination During Feed Manufacturing. Poster presented at the 48^th American Association of Swine Veterinarians’ Annual Meeting. 2017;241.