Enhanced feed safety on farms ensures serenity in uncertain times

Written by Romain D’Inca, Category specialist MCFA

Pig production faces permanent economical, social and geopolitical challenges, with limited possibilities of control by farmers. Focus on controllable parts of producing units such as feed safety is then critical. For viral contaminations, occurrence, severity and pathogen involved can’t be predicted. Medium-chain fatty acid can help in the control of such risks when feed supply to animals is concerned.

While acceleration used to be considered as a buzzword, it must now be seen as a synthetic descriptor of today’s volatile, uncertain, complex and ambiguous world. As an example, the latest yearly reports of WTO and FAO confirmed respectively that uncertainty of trading rules so as protectionism on the one hand, disbalances in food production and allocation on the other hand, are growing risks for food chain worldwide, with almost unpredictable long term consequences. Specifically in our Agricultural sector, land and raw material availabilities are jeopardized by climate change; currencies’ rate, trading and supplies are affected by geopolitical tensions; more frequent investments are needed to comply with constraining regulations on the producing areas or their target markets; … Those are only few examples of the numerous factors impacting farmers with limited or no possibilities for them to influence.

It means that with the objective to maintain high standards of production in an economically-relevant way, time and energy of farm operators must be focused on items they can monitor and optimize. Obviously: adequate management, high quality of nutrition and complete biosecurity can be considered. The latter is of paramount importance when it comes to technical results in Swine production. Minimizing biosecurity risks can include for instance adequate washing or disinfection of people and machines. Quarantine for livestock or pest control against rodents, birds and insect can be set-up. Adequate air filtration and water disinfection strategies can be implemented. But what about the risk of pathogen transmission via the feed ? In the case of viruses, some reference studies such as Niederwerder et al., 2019 confirmed that, even when feed is contaminated at low levels with a virus, the high frequency and direct contact with animals in the feeder make the feed a more important risk factor for transmission than water or other biosecurity items. Consequently, mitigations measures against viral pathogens in the feed must be implemented, this in respect of local regulations that less and less allow the use of chemical mitigants that can be at risk for operators from feed mills to barns.

Medium-chain fatty acids as a natural solution against virus-associated risks

Medium Chain Fatty Acids (MCFA) are molecules available naturally, for instance in coconut oil. Those molecules are used today in food, nutraceutical and pharmaceutical industries for their proven action against various types of pathogenic microorganisms. Because MCFA action includes the damaging of phospholipid by-layers of potential pathogens, we developed in the last years a blend of free-MCFA (Feedlock, Royal Agrifirm Group, The Netherlands) specifically optimized in vitro against enveloped viruses (Tran et al. 2021) and we investigated further the impact of this blend using a model mimicking natural contamination with multiple viruses to animals using the “ice-block challenge” model described by Dee et al., 2021.

Shortly, experimental set-up consisted in preparing 1 lbs ice blocks (-80°C) loaded with several viruses such as PRRSv, PEDv, and SVAv (Seneca virus, the only non-enveloped virus of this test) at 105 TCID50/ml x 100ml each. Those blocks were dropped in feed bins at start and after 6 days of the experimental period, permitting a progressive release of the viruses in the feed along the provision to animals. A total of 12 pens of 7 to 8 weaned pigs were used, half of them being fed the contaminated diet alone (Control), the other half being fed the same diet supplemented with Feedlock MCFA (Royal Agrifirm Group, NL). Clinical scores (dyspnea, weight loss and rough hair coat for PRRSv, diarrhea for PEDv and lameness for SVAv) and relevant post-mortem sampling of biological compartments (e.g serum for PRRSv, rectal swabs for PEDv and tonsils for SVAv) were performed. Additionally, presence of the viral RNA particles was detected using dedicated PCR procedures in the feeder, so as in chewing ropes available for the pigs in the different pens, in order to assess the link between feed and oral contamination of pigs.

Supplementation of the contaminated feed with the MCFA blend was associated to the absence of morbidity signs in the related pens, while 1 or more animal per pen expressed morbidity in the Control group (Figure 2, left). Similarly, autopsies confirmed the absence of signs of infection in the target biological compartments of pigs fed with MCFA compared to Control group for PRRSv and PEDV. In this test, the infectivity of SVAv appeared insufficient to really conclude on the impact of MCFA (Figure 2, right). Those very discriminating results confirmed that incorporation of MCFA in the feed exerted a preventive effect against the PRRSv, PEDv and SVAv associated symptoms.

We therefore analysed the presence of viral RNA in the feeder and in the saliva of the pigs, in order to validate that the lower impact of viruses at the animal level resulted from the MCFA action on the viral particles at the feed level, minimizing as a consequence the risk for pigs to be exposed to the viruses at the feeder levels, where the interaction between the feed, the pathogens and the animals are the most likely to occur.

Results: viral RNA in feed and saliva

Similarly to what was observed at the pig level, no viral RNA was detected 15 days post-infection (dpi) for any of the virus tested in the MCFA-supplemented group, whereas RNA particles were detected in all the control samples at feeder or saliva levels. Interestingly at 6 dpi, some viral DNA could be identified also in the MCFA-supplemented group while this was not associated to morbidity nor symptoms in the animals. This can be explained by the fact that in this study, we did not checked for the complete viral particles, but for RNA using PCR. Target of the MCFA action being the phospholipid envelop of the virus and not the nucleic acids. With a half-life from minutes to hours for RNA and ice-blocks’ contaminations at d0 and d6, it is not surprising to still detect those nucleic acids in samples taken at 6 dpi, even when the virus envelopes are destroyed.