By Laura Greiner, Iowa State University
Feed mills, nutritionists and producers alike worked to better understand the potential of feed ingredients to serve as a fomite after the arrival of Porcine Epidemic Diarrhea Virus (PEDv) into the U.S. in 2013. Since that time, multiple researchers have documented the potential for ingredients to transport viruses such as PEDv and African swine fever (ASF) as well as potential mitigation steps that can be taken to reduce this risk. However, with these different programs, there can be potential nutritional challenges that must be understood.
Here are four current mitigation programs and the potential nutritional challenges that need to be managed.
1. Extended storage: The nature of viral infectivity is that in the course of time, the virus naturally is killed by the environment through various enzymes and other factors that either degrade the DNA/RNA or destroy the viral membrane. Holding feed or feed ingredients for long periods of time allows for the natural destruction of the virus and can be a relatively low cost option for many. Recent work suggests that viruses like PEDv may be present for a period of time, but other viruses such as ASF, could be present for months. If the product being held is a complete feed or a vitamin and mineral pack, the degradation of vitamin over time could be a challenge. Additionally, vitamin packs with choline or inorganic minerals have the potential to further degrade vitamins due to oxidation or additional moisture. In general, vitamin packs should be used within 3 months of manufacturing and vitamin and mineral premixes should be used within 2 months to reduce this risk.
2. Extended storage plus heat: Vitamins are susceptible to degradation when exposed to elevated temperatures for extended periods of time. Today, it is common practice to hold vitamins, premixes or bagged products in a warehouse for a period of two weeks or longer. With the concern of ASF entry into the U.S., some may be considering adding temperature into the equation to reduce the period of storage and minimize the space required to hold ingredients. With this, certain vitamins that are heat sensitive such as vitamins A, B12, folic acid and pyroxidine could be a concern.
3. Feed disinfection: Using products that are formaldehyde based or contain medium chain fatty acids have been shown to be effective in bacterial control against organisms such as Salmonella. Recent publications indicate that these have the potential to be effective against viruses as well. Work conducted in the last three to four years suggest that some of these products have the potential to reduce amino acid and vitamin availability to the animal and that reduction may impact growth performance of the animal.
4. Further feed processing: Pelleting diets has the potential to reduce pathogens on the surface due to the higher pelleting temperature. Pelleting feed at higher temperatures or longer periods has the potential to destroy vitamins, enzymes such as phytase, or cause an off flavor in the feed. Using heat-stable phytase can reduce the potential loss of phytase activity.
While nutritionists take many of these factors into consideration to prevent issues such as a vitamin deficiency, additional challenges in the barn such as high iron in the water or a disease outbreak could have the potential to create a deficiency if nutrient levels are marginal due to a handling change to prevent disease transmission in the feed. Regardless of what method is chosen, ingredients and premixes should be stored in cool, dark, and low-humidity facilities as much as possible. As changes are made to continue to improve biosecurity around the feed mill, continue to work with your nutritionist to manage these challenges.
Laura Greiner is an assistant professor in animal science at Iowa State University where her focus is on swine production and nutrition.
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