In the US, nobody needs to be told about the risk of viruses entering a farm through feed. Years of research have proved this for swine producers. But what can be done? Scientists have investigated the effect of additives on mitigating the transmission of viral diseases through feed. “It is exciting that producers and veterinarians now have options for use in a feed biosecurity programme.”
Results from a new collaborative study have recently been published in the journal Transboundary and Emerging Diseases, in which 15 commercial additives were tested to evaluate their effect on mitigating Senecavirus A (SVA), Porcine Epidemic Diarrhoea virus (PEDv) and Porcine Reproductive and Respiratory Syndrome virus (PRRSv) in contaminated feed. A wide range of organic substances were tested, from essential oils and monovalent or multivalent organic acids to short, medium and long-chain fatty acid blends and formaldehyde-based products.
“In 14 of the 15 additives tested, pigs on the supplemented diets had significantly greater average daily weight gain, significantly lower clinical signs and infection levels, as well as numerically lower mortality rates compared to the control pigs,” says Dr Scott Dee, director of applied research at Pipestone Veterinary Services in Pipestone, MN, United States. Dr Dee conducted the study with several colleagues at Pipestone, Dr Megan C. Niederwerder at Kansas State University and Dr Aaron Singrey and Dr Eric Nelson at South Dakota State University (Dee is also an adjunct faculty member there).
It is important to note that the products tested in this study do not yet have label approval claiming efficacy against viruses
“We concluded that these additives mitigated the effects of the three viruses we investigated in contaminated feed, resulting in improved health and performance compared to pigs fed non-mitigated diets,” says Dr Dee. “It is exciting that producers and veterinarians now have options for use in a feed biosecurity programme. However, it is important to note that the products tested in this study do not yet have label approval claiming efficacy against viruses. Many companies are collaborating with the FDA to move this forward.”
The effects of several of these feed additives in combating African Swine Fever virus (ASFv) are currently being carried out by Dr Niederwerder at her lab facility, which is certified to handle this virus.
This study builds on findings (from the same group of researchers and others) that have demonstrated that these same pig viruses can survive in feed. The capability of livestock feed to transmit viral diseases was first proven scientifically by Pipestone in 2014 during the PEDv epidemic in North America. “Since that time, various feed additives have been evaluated in lab settings for their effect on viral viability and infectivity in contaminated feed using bioassay piglet models,” Dr Dee explains.
“However, studies that involve the real-world conditions of commercial swine production were needed, with larger populations of pigs, realistic volumes of contaminated feed supplemented with selected additives and natural feeding behaviours.”
Dr Dee and his colleagues used a new research model called an “ice block challenge” to insert equal concentrations of SVA, PEDv and PRRSv into feed treated or not treated with additives. The ice blocks were then manually dropped into designated feed bins and the pigs were allowed to consume the feed naturally.
PEDv broke out in the US in 2013, and its movement into Canada in 2014 was traced back to a contaminated feed ingredient. In subsequent years, members of the Canadian Pork Council worked with staff at the Canadian Food Inspection Agency (CFIA) to create national guidelines for the import and handling of feed ingredients that present high risks for viral diseases such as ASF, along with storage time and heat treatment recommendations for industry. Much of this was launched in the spring of 2019. Regarding what has been happening in this vein within the US, Dr Dee says the pork and feed industries there have worked very hard over the last few years and have been successful in making changes to biosecurity at feed mills.
“There are strong industry programmes now in place, but I and others would like to see a national government-led pig virus disease prevention and control programme pertaining to feed, similar to what is happening in Canada,” Dr Dee says. “We need a national government-driven programme with additives approved by the Food and Drug Administration (FDA) and standard operating procedures for storage time, handling and so on.”
We will hopefully be able to set short-, intermediate- and long-term goals to get a programme going
He adds, “We’ve had good leadership from industry, and we scientists are building a body of evidence on which a sound national programme can be based. A national Feed Risk Taskforce has been formed, and I sit on it with staff from the US Department of Agriculture; FDA; Swine Health Information Council; National Pork Producers Council; CFIA; members of the poultry, swine, cattle and feed industries, and others; and we are meeting this month (September 2020). We will hopefully be able to set short-, intermediate- and long-term goals to get a programme going and discuss future research directions.”
Dr Dee adds that, in the meantime, now that he and his colleagues have provided the industry with efficacy data, it is up to individual feed companies and producers to make mitigation decisions based on cost, mill specifications and so on. “We have discovered there are lots of additive options for viruses of domestic interest, such as PRRSv, PEDv and SVA,” he says, “and we look forward to data from Dr Niederwerder’s lab regarding the effect of these products in combating foreign animal diseases.”