Brian Aldridge 2015-02-23 23:29:50
My parents gave me an appreciation of food production through their stewardship of the land, crops, and animals that have been their source of income and contentment for 70 years. My exposure to livestock production in the beautiful Wiltshire countryside of southern England was the foundation for my career in food animal health and production. As a veterinarian, I have contributed to an abundant, safe, and healthy food supply through my work as a clinician, researcher, and educator. In the 1960s, when I was young, there were few concerns about food production in the U.K. Livestock production was based on low-technology rearing systems with relatively low levels of infectious disease. Since then, the U.S. livestock industry has developed a high fixed cost, low operating cost, low margin production system based on animal confinement and the widespread use of antibiotics. Because of its ability to produce animal-based food at a low cost, this production model has been adopted around the world, particularly in emerging economies seeking to meet their own protein needs. As a result, the sustainability of global animal-source food production is entirely dependent on the constraint of infectious disease, and therefore completely reliant on antibiotics. Due to public health concerns about antimicrobial-resistant infectious agents, the U.S. Food and Drug Administration (FDA), and equivalent agencies in Europe, are now implementing voluntary plans with industry to phase out the use of certain antibiotics in food animals. Inevitably, widespread antimicrobial use will disappear from food production systems due to public demand and policy changes. The industry will then be faced with the staggering challenge of maintaining efficient production without the freedom to employ antibiotics to manage infectious disease. When this postantibiotic era becomes a reality, it will present a great risk to the security and sustainability of global food production through a reduction in production efficiency. It also means that livestock will more likely be managed in ways that further burden our environmental resources. So how can we modify our approach to livestock management, and refashion our antimicrobial practices, in a way that preserves the security and safety of our food supply? Antimicrobial use in livestock systems is almost exclusively directed at removing or preventing disease by specific pathogens. This focus on infectious disease control by minimizing contact with or destroying bacteria is based on the successful reductions in morbidity and mortality achieved with antimicrobial practices over the past century. While this has clearly been a successful strategy, it has also led to a pathogen-centric view of microbes. This demonization of microbes has slowed somewhat in recent years due to the many studies showing that the microbiome, the community of beneficial commensal microbes, coexists in a symbiotic relationship with its host, enhancing the host’s health and productivity by preventing the expansion and colonization of harmful microbes. Microbial colonization of host mucosal surfaces begins early in life, following the acquisition of pioneer organisms from the mother. There is considerable variation in the composition of the microbiota during the first years of life, but the most desirable trajectory is toward richness and diversity. The drivers of the microbiome fall into broad categories related to the host (e.g., genome and epigenome), the environment (e.g., temperature and humidity), and system inputs (e.g., nutrition, housing, and hygiene). This process is strongly influenced by management factors (including antimicrobials), and it is tightly linked to the host’s immune system. It is evident that a healthy microbiota serves a vital role in establishing immune competence and, conversely, in precipitating incompetence and dysfunction when disturbed. There is also compelling evidence that antimicrobials exert an effect beyond pathogen eradication by influencing the ecology of the microbiome, and subsequently altering the host’s metabolism, as well as the development of antimicrobial resistance. These effects of antimicrobials on the host microbiota likely persist for life. Our use of antimicrobials in animal health management could be transformed by a broader understanding of the beneficial role of microbes in livestock health. This could begin with a new appreciation of livestock-based food production systems as complex, multi-organism ecosystems, the efficiency and productivity of which depend on potentially fragile interactions between different ecological communities—animals, microbes, and people—and their environments. This change in mindset, away from the idea of microbes as a primary cause of poor health and instead seeing microbial communities as a reflection of our success in ecosystem management, would transform our current approach to enhancing the efficiency of livestock-based food production. The host organisms—ourselves and the animals we raise—are microbial ecosystems within the greater ecosystem of the production system. We need to understand the impact of various management practices and environmental designs on host-microbe interactions. Only by understanding the ecology of the food production system can we identify and design sustainable strategies for optimizing livestock health and productivity in particular, strategies that are not dependent on the widespread use of antibiotics. Brian Aldridge, Clinical Professor, Department of Veterinary Clinical Medicine, University of Illinois at Urbana-Champaign, USA; email@example.com. Top border Lamica | Dreamstime. Mid-page illustration by Kerry Helms, College of Veterinary Medicine, University of Illinois at Urbana-Champaigna, USA.
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