The Holobiont concept in ruminant physiology - more of the same, or something new and meaningful to food quality, food security, and animal health?

The holobiont concept has emerged as an attempt to recognize and describe the myriad interactions and physiological signatures inherent to a host organism, as impacted by the microbial communities that colonize and/or co-inhabit the environment within which the host resides. The field acknowledges and draws upon principles from evolution, ecology, genetics, and biology, and in many respects has been "pushed" by the advent of high throughput DNA sequencing and, to a lesser extent, other "omics"-based technologies. Despite the explosion in data generation and analyses, much of our current understanding of the human and ruminant "holobiont" is based on compositional forms of data and thereby, restricted to describing host phenotypes via associative or correlative studies. So, where to from here? We will discuss some past findings arising from ruminant and human gut microbiota research and seek to evaluate the rationale, progress, and opportunities that might arise from the "holobiont" approach to the ruminant and human host. In particular, we will consider what is a "good" or "bad" host gastrointestinalmicrobiome in different scenarios, as well as potential avenues to sustain or alter the holobiont. While the holobiont approach might improve food quality, food security and animal health, these benefits will be most likely achieved via a judicious and pragmatic compromise in data generation, both in terms of its scale, as well as its generation in context with the "forgotten" knowledge of ruminant and human physiology.