With the introduction of the Veterinary Feed Directive (VFD), low dose antibiotics are no longer included in livestock feed, including pigs. Researchers are trying to determine alternative feed supplements that will help battle pathogens in farms and research settings by learning more about how the gut microbiota may serve as alternatives to in-feed antimicrobials. The gut microbiome is a fluctuating microbial population that influences gut integrity and the ability to protect the body from harmful pathogens and prevent undigested food from being absorbed in the intestines.
The microbiome and host have an interdependent relationship and an imbalance of microbes during times of stress, such as weaning, causes susceptibility to disease. Interactions between dietary nutrients and gut microbes are critical to the digestion and absorption of nutrients, which contribute to the strength of the the host’s gastrointestinal tract. Providing the host with substrates that nourish gut microbes, (i.e., prebiotics) may lead to production of compounds that contribute to health status.
Research at the University of Nebraska-Lincoln has been focusing on the contribution of isoflavones, a compound found in soy, to the immunity and growth of nursery piglets. Isoflavones are structurally similar to estrogen, giving them the ability to bind to estrogen receptors (ER) and either increase estrogen hormone responses or prevent them. They have been shown to disrupt cellular activities, causing the mutation that results in uncontrollable cell division, developing cancer. They also possess antiviral and anti-inflammatory properties of interest since they reduce the infectivity of viruses as well as keep the body functioning normally during stressful periods.
In a recent nursery pig experiment, piglets were fed four diets with supplementation of isoflavones and samples were collected to analyze circulating anti-inflammatory factors in the blood. In addition, fecal samples were obtained to evaluate gut microbial populations and potential effects on gut health. There were no difference in the anti-inflammatory factor circulating in the blood, however diet did prove to alter the gut microbiome with an increase in Ruminococcaceae, an abundant microbe with beneficial effects on gut barrier function in the diets including isoflavones. Growth performance was not affected by isoflavone supplementation and future analyses are planned to look more closely at the changes in the gut microbiome.
Collaboration with Dr. Hiep Vu is underway to put isoflavones to the test when challenged with a virus in a cell culture model. A cell line cultured from the small intestine of a neonatal piglet will be challenged with transmissible gastroenteritis virus (TGEV), a common rotavirus that causes diarrhea and vomiting in both young pigs and humans. The cells will be infected with the virus after treatment with the isoflavones and samples will be collected to measure intestinal integrity and circulating immune parameters, as well as the capability of the isoflavones to help the host prevent infection.
Further research will include a disease challenge where nursery piglets will be fed varying concentrations of isoflavones and immune response and microbiome composition will be observed. This will tell us how supplementation of isoflavones impact the gut microbiota and if this can be correlated to the prevention of disease spread. Another experiment will include fecal samples from swine farms across the Midwest to determine what proportion of pigs are able to digest isoflavones into certain products of interest, such as S-equol. Soy is popular in Asian diets and less prevalent in typical Western diets, so it is unknown how well Americans might be able to digest the soy product if the necessary microbes are not present.
The interest in the microbiome and gut health is a topic that could benefit swine and humans alike as these studies could serve as the forefront for human nutrition and identify isoflavone contribution to the immune system.
By Sydney Kinstler, Dr. Phillip Miller, Dr. Thomas Burkey, Dr. Samodha Fernando, and Dr. HiepVu