FEED ADDITIVES ▶▶▶
Mitigating virus in pig feed
It was in 2014 that the North American veterinary community – as well as the worldwide feed and pork industries – started to realise that viruses were being transmitted in feed.
BY TREENA HEIN, CORRESPONDENT P
orcine epidemic diarrhoea (PED) broke out in the United States in 2013 and by January 2014, the dis- ease had arrived in Canada. “We figured out quite quickly at that point that the outbreak here in Cana-
da was linked to a certain feed ingredient, from the same feedmill, and soon thereafter a research paper was published by scientists at the National Centre for Foreign Animal Dis- ease in Winnipeg Manitoba that showed the link was possi- ble,” explains Dr Egan Brockhoff, veterinarian at Prairie Swine Health Services in Red Deer, Alberta and veterinary counsellor for the Canadian Pork Council.
“Then African Swine Fever (ASF) came along and since then in the US, Dr Scott Dee, Dr Megan Niederwerder and Dr Cassan- dra Jones and others have done a lot of work to look into how viruses can tag along in feed ingredients being shipped all over the world.”
What’s been discovered Among the many other studies, Dr Dee (of Pipestone Applied Research at Pipestone Veterinary Services in Minnesota) and colleagues had published an evaluation in 2018 of the survival
How various additives inhibit viruses
Organic acids can directly inhibit virus activity, for example by suppressing gene expression. They can also prevent viruses from attaching to the surface of host cells. (In bacteria, organic acids are able to cross the membrane and cause dis- ruption by changing the concentrations of charged atoms.) Fatty acids can af- fect the virus coating, causing leakage or total disintegration of the envelope. Some essential oils (e.g. eucalyptus, tea tree and thyme) can directly inactivate free virus particles.
8 ▶ ALL ABOUT FEED | Volume 28, No. 5, 2020
of livestock viruses in animal feed ingredients that were, and still are, imported daily into the US. The study involved simu- lated transboundary shipping conditions and eleven diseases of global significance: Foot and Mouth Disease, Classical Swine Fever, ASF, Influenza A of Swine, Pseudorabies, Nipah, Porcine Reproductive and Respiratory Syndrome (PRRS), Swine Vesicular Disease Virus, Vesicular Stomatitis Virus, Por- cine Circovirus Type 2 and Vesicular Exanthema of Swine Vi- rus. For six viruses, it was possible to use surrogates with simi- lar genetic and physical properties but for the others, actual viruses had to be used. “We found that more viruses survived in conventional soybean meal, lysine hydrochloride, choline chloride, vitamin D and pork sausage casings,” says Dr Dee. “These results also supported data already published on the risk of transporting PEDv in feed.” By 2019, US Department of Agriculture scientist Dr Rebecca Gordon and her colleagues had published a review of studies published up to March 2018 (including the study by Dr Dee and his group) called ‘The Role of Non-animal Origin Feed Ingredients in Transmis- sion of Viral Pathogens of Swine.’ In their analysis, Dr Gordon and her team concluded that whilst some critical questions pertaining to transmission of swine viruses via feed and feed ingredients have been addressed, further investigation is needed into how viruses are transmitted via feed to swine under actual field conditions. On that note, Dr Dee and his colleagues are preparing to publish results of a project where virus survival was tested by placing them in feed and driving the feed around the country for 21 days to simulate in-coun- try transport conditions. The viruses used were PRRSv and PEDv and Senecavirus A, pathogens which Dee’s lab is certified to handle.
Awareness to action Because of all the research into viral survival and transmission in feed since 2015, Dr Brockhoff says the world’s pork and feed industries have become very aware of how viruses can survive in and be transported in all sorts of different feed in- gredients. “With my colleagues at the Canadian Pork Council (CPC), we went to the Canadian Food Inspection Agency (CFIA) with all the research in 2018, and we worked together to come up with changes in how high-risk feed ingredients such as unprocessed grains, oilseeds as well as associated meals destined for use in livestock were imported into
PHOTO: RUBEN KEESTRA
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