“Gut health” and antimicrobial resistance

Gut health and maintaining optimal structure and function of the gastrointestinal(GI)  tract is necessary to achieve sustainable and cost-effective pig production.

The gastrointestinal tract is responsible for regulating physiological homeostasis that provides the pig with the ability to cope with infectious (e.g., enteric pathogens) and non-infectious (e.g., production stressors) challenges.

What does the term ‘gut health’ mean?

‘Gut health’ is a commonly used term that attracts a lot of attention, although a clear definition of this expression seems to be missing. However, generally speaking, according to Pluske et al. 2018:

➢digestion and absorption of nutrients.

➢ metabolism and energy generation

➢ a stable and appropriate microbiota / microbiome

➢defense mechanisms including barrier function and immune mechanisms of the mucosa

➢ and interactions between these components

Due to the profound changes in (GI) tract structure and function associated with the post-weaning transition, “gut health” in piglets is of great interest for pig production.

The inclusion of antimicrobial compounds, in diets and (or) in water, including antibiotics, kill microbes or inhibit their growth which helps piglets during this period of change. Reducing the impacts of post-weaning growth control.

However, the need to implement different feeding strategies and (or) include feed additives (e.g. Pew Charitable Trusts, 2017) due to bans/reductions in the use of certain antimicrobial compounds in some parts of the world have placed greater emphasis on the ‘healthy gut‘ concept.

A deterioration in the pig’s intestinal health due to the presence of enteric diseases after weaning can be directly related to a decline in the animal’s overall  health. Although some direct relationships may be established between the performance and efficiency of the pig and a “healthy” GI tract, sometimes this connection is more subtle and less obvious.  Especially in the absence of evident enteric diseases (Pluske et al. , 2018).

One of the keys to understanding ‘gut health’ is the microbiota, i.e. the ecological community of commensal microorganisms, symbiotics and pathogens that inhabit the gastrointestinal (GI) tract.

It should be noted that, as a synonym, microbiome describes the collective genomes of microorganisms that reside in the GI tract or the microorganisms themselves.

Although the term microbiome technically refers to the population of bacteria, yeasts, fungi, viruses, and protozoa within an ecosystem, the term is often widely used only to refer to bacterial composition.

However, the appropriate terminology when the exploring bacterial population is microbiome or bacterial microbiota.

The sweeping of the bacterial microbiome in pigs and their complex interactions with the host and external environment (e.g., through diet or through the environment) is a relatively new phenomenon. Which is largely driven by the increasing availability and lower cost of new genomic sequencing technologies.

Research on the GI tract microbiota of pigs has a new and more urgent perspective due to the previously mentioned bans/reductions on antimicrobial compound use for pig production. This highlights the need of maintaining a healthy GI microbiota in key fields of interest with various stressors and infectious diseases. (Brüssow, 2017).

However, some antimicrobial compounds are still allowed in some countries around the world. Which has created a parallel area of interest (and concern) regarding the ability of numerous members of the GI tract microbiota of exhibiting resistance against some antimicrobial compounds. Especially against antibiotics known as (CIAs),  critically important antibiotics – which are also used in human medicine.