ISSUE FOCUS FEED & ADDITIVE MAGAZINE April 2022 31 THE IMPORTANCE TO BOOST NATURAL IMMUNITY Enough reason for pig producers, veterinarians and nutritionists to search for strategies to control or eliminate the virus from infected herds. Adapting farm management and implementing biosecurity measures is crucial to control the disease to a certain level and can be supported by vaccination. However, on ‘problem’ farms, a strategy with feed additives that supports natural body defences might be necessary to control PRRS. FRA® C12 seems to be a perfect fit in such immune boosting strategy as the product has both a direct and indirect antiviral effect. This feed additive is based on glycerides of lauric acid, the saturated fatty acid with 12 C-atoms. FRA® C12, both in liquid and dry form is developed and produced by FRA®melco. Direct antiviral effect Besides their well-documented antibacterial effect, scientific literature suggests that lauric acid and its glycerides (main components of FRA® C12) have antiviral properties specifically against persistent fat-enveloped viruses, like HIV, Influenza virus and PRRSv. Lauric acid glycerides are found to attack the viral lipid membrane causing severe leakage. Higher concentrations might even lead to the complete breakdown of the viral envelope and the viral particles. When it comes to antiviral effects, lauric acid and its glycerides always stand out. In vitro work by Thormar et al. 1987 already showed that lauric acid is active against the enveloped Vesicular stomatitis virus (VSV), see Figure 1. However, monolaurin proved to be active as well, but at a concentration which was 8 times lower compared to lauric acid, confirming its stronger antiviral activity compared to free lauric acid. An interesting review on lauric acid and lauric acid glycerides by Lieberman et al. 2006 also pointed out the unique antiviral properties of specifically the glycerides which turn out to be more biological active compared to free lauric acid alone. Indirect antiviral effect - supporting body defence Next to the direct antiviral properties of glycerides of lauric acid, also indirect effects could be expected. Research conducted by FRA®melco in cooperation with universities and other research facilities, has shown that FRA® C12 has a modulatory impact on the host inflammatory responses. This seems to be of high importance to support the elimination of infections. In broilers the product has also shown to increase the level of antibodies against the highly contagious virus disease Infectious Bronchitis (IB). This might increase the level of protection against an IB challenge. Overall, it can be concluded that lauric acid glycerides strengthen the immune response and show direct antiviral effects, explaining their increasing popularity at farms facing viral challenges. PROOF OF CONCEPT Back to pigs. To study if FRA® C12 Dry could help controlling PRRSv, a trial was conducted at a commercial farm in Belgium, suffering from a severe PRRSv outbreak and encountered problems with Streptococcus suis in the past. Therefore, the farmer vaccinated his sows against Streptococcus suis, but not against PRRSv. During the trial sows received FRA® C12 in their lactation diet from one day before farrowing till weaning. Weaned piglets received FRA® C12 in their diets during the entire nursery period. Figure 1: Antiviral effect of different glycerides and the corresponding free fatty acids (Adapted from Thormar et al., 1987)
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