The importance of early microbial exposures in pigs: The microbiome nexus

Interest in the microbiome-the community of diverse bacteria, fungi, microeukaryotes and viruses that colonize animal and environmental surfaces-has become mainstream in the swine production field. The premise, given the critical influence of the microbiome in the animal physiological landscape, is that manipulating or targeting these microbial communities along the pig anatomy could favorably alter productive and sanitary goals in swine production systems. To that end, a myriad of dietary manipulation strategies (largely based on feed additives) have been proposed, which acquire significant value as the ban of growth promotion antibiotics becomes a reality worldwide. However, the success of such strategies in promoting pig growth and robust health has proven to be inconsistent, at least in comparison with the standard use of antibiotics for growth promotion. In this chapter, we take a step back to discuss the importance of the events that lead to the very first microbiome seeding (or establishment) in the pig, specifically, placing critical importance on the maternal environment. We discuss how different maternal (e.g. milk, vaginal canal, skin) and environmental (farrowing surfaces) microbial sources contribute to the primordial microbiome of newborn pigs and highlight the interplay between early microbial seeding events and an immature immune system as a key modulator of pig physiological performance along the life course. We also propose the need to consider manipulating early microbial seeding mechanisms, besides nutritional or feed additive strategies, to boost pig physiological performance along its productive cycle.