New findings reveal that FRA® C12, known for its antiviral activity, could help support natural body defence. It improved sow and piglet performance on a farm suffering from a severe PRRSv outbreak. In the study, conducted by FRA®melco, the addition of FRA® C12 Dry to the diet resulted in a reduced pre-weaning mortality, lower use of medication and significantly reduced PRRSv shedding in weaned piglets.

Head of R&D
FRA®melco B.V.
Sow productivity has increased tremendously during the last decades and brought some serious challenges with it, like sow longevity and the viability and uniformity of piglets. Moreover, porcine reproductive and respiratory syndrome virus (PRRSv) is still one of the most relevant viruses affecting pig farming, causing variable clinical signs. Sow farmers commonly face a substantial increase of abortions, number of stillbirths, pre-weaning mortality and respiratory diseases in weaners and growers. In addition, in PRRSv-infected pigs the susceptibility to secondary bacterial or viral infections increases dramatically. For instance, concurrent infections with Streptococcus suis are often reported. The prevalence of secondary infections together with direct losses caused by PRRSv are the reason for the major economic impact of this viral syndrome.
HOW PRRSv SABOTAGES THE IMMUNE SYSTEM
Like all viruses PRRSv needs host cells to multiply. The virus inserts its genetic material into the host cell and hijacks its machinery to create many viral copies. One of the main target cells for PRRSv replication are porcine alveolar macrophages, found in the lungs. These macrophages are big white blood cells that ‘eat’ foreign material, like bacteria and viruses, and remove dead cells. They serve as the first line of defence against inhaled harmful microbes. When attacked by PRRSv their function is directly impaired.
Moreover, in PRRSv-infected animals the production of pro-inflammatory cytokines, which signal the immune system to do its job, has shown to be limited. The reduced level of these important messengers allows the PRRS virus to escape from the host immune response. Hence, the immune system is not fully activated, and viral clearance is not initiated. It allows PRRSv to multiply easily inside the host, like sows or piglets. This immunosuppressive effect of PRRSv may also contribute to the increased risk of secondary infections, like Streptococcus suis.
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 wturn 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.
Lower pre-weaning mortality
A change in farm-management resulted in an inconsistency in number of days in the nursery house, the researchers of FRA®melco could therefore not compare all sow and piglet data. However, the farmer was satisfied with the general improvements seen in the treatment group as compared to the control group. From the data that could be compared, it was concluded that pre-weaning mortality was reduced from 14.1% in the control group to 10.0% in the treatment group; a reduction of 29 percent. It might be suggested that suckling piglets of sows receiving FRA® C12 in their lactation diet got extra immunity via the colostrum and milk.
Less PRRSv infected piglets
The researchers also measured the severity of the PRRSv infection by screening saliva on virus excretion. They collected saliva samples from chewing ropes in randomly chosen pens. A week after weaning, 20% of the pens in the control group were tested positive for PRRSv. This increased to even 70% at day 37 after weaning, indicating a serious infection. In the treatment group 10% of the pens were tested positive for PRRSv after 7 days, which was only slightly increased to 20% at day 37 (see Figure 2). Hence, FRA® C12 seemed to be a very interesting and promising tool assisting directly and/ or indirectly in the viral clearance of PRRSv.

Less medical treatments in piglets
Next to the problems with PRRSv the farm struggled with locomotor problems in weaned piglets most likely due to Streptococcus suis infections, a significant disease in intensive, indoor swine operations. Interestingly, in this trial weaned piglets in the treatment group received a lower number of individual injections against locomotor problems as compared to the control group: 1.9 versus 3.2 treatments/100 piglets respectively. The reduction was near significantly different (P=0.052). Hence, FRA® C12 Dry seemed to have suppressed the susceptibility to secondary infections with Streptococcus suis.
CONCLUDING REMARKS
Feed additives based on glycerides of lauric acid, like FRA® C12, are gaining popularity in broiler and pig farming, especially when it comes to fight viral challenges. Glycerides of lauric acids can directly attack virus particles or stimulate the immune system of the host, making them more capable of fighting against viral challenges. The results of the current study showed that FRA® C12 has beneficial effects on a farm suffering from a severe PRRSv outbreak. The farmer was satisfied with the obtained improvements.
Although the exact mode of action is currently not yet fully understood, FRA® C12 seems to be an interesting and promising tool assisting in the viral clearance of PRRSv and in controlling the risk for secondary infections in PRRSv-positive pigs.
References are available upon request via R&D at Framelco.
About Olga Dansen
Graduated as Animal Scientist from Wageningen University in 2012, with a specialization in animal nutrition. After working in the industry for several years she joined FRAmelco in 2015. In 2016 she became Head of R&D.