Gut Health In Pullets And Laying Hens.

In 2030, expected global population growth is estimated at 8.6 billon people (UN, 2017). In turn, global demand for food will increase with an estimated growth in egg production of 50% between 2015-2035. (FAO; OECD; Rabobank; FAPRI © Statista 2018).

In this sense, genetic selection during the last years has provided hens with a higher production capacity. Gut health is a key factor in achieving maximum productive potential, not only because it’s a key factor for digestion and the absorption of nutrients but also because it’s an essential component of the bird’s immune system.

Concerns are also growing among consumers on the use of antibiotics in relation to microbial resistance.

This, along with pressure from a demand in increased welfare and food standards in particular from the increase of cage free production would lead us to a strong emphasis and focus on the challenges of maintaining a healthy gut.

Several factors must be considered about Gut health (Graph nº1)

Graph 1. Factors affecting gut health.
  1. Feed and water. Both vectors create a connection between the external and internal environment of the hen, increasing the possibility of a negative effect on the intestinal balance.

Some common influences:

  • Anti-nutritional factors (non starch polysaccharides and anti-trypsic factors),
  • Water, raw material and feed contaminants (E. Coli, Salmonella, mycotoxins, etc…),
  • Sudden changes in formulation or,
  • High density diets – excess of nutrients.
  • Bird physiology. How different organs and the endocrine system respond against challenges.
  • Gut microbiota. Represented by the balance between pathogenic and commensal flora. Latter being the one involved in the development of intestinal morphology and structure, immune modulation and supporting digestion and absorption processes.
Graph 2. Effect of mycotoxins on gut integrity. Cheng et al., 2012. Gut integrity is affected by increasing deoxynivalenol (DON) concentration in feed.

Strategies for gut health maintenance.

The best practice to maintain an optimal gut health and therefore the hen’s productivity is PREVENTION.  Some aspects to be considered are:

  • Proper management, hygiene and biosecurity
    • Optimal feed quality, format and presentation
    • Water quality. Monitoring water to feed ratio would act as an indicator.
    • Establishing adequate vaccination programs
    • Reduction in crude protein levels may help to reduce undigestible protein fermentations. Inclusion of synthetic amino acids and proteases will help to control these undesirable fermentations.
    • Feed additives

The recent focus on reducing or restricting the use of antibiotics has been accompanied by a rise in  intestinal problems often leading to a loss of productivity that has led to the development of several feed additives with the potential to exert beneficial effects on intestinal microbiota, impede pathogens adhesion to epithelial cells and to improve the immune response. The market is now awash with probiotics, prebiotics, organic acids and blends of them (either protected or not), phytobiotics and existing feed enzymes. Always remember that the efficacy of feed additives relies on additional factors such as age of the hen, management, production system, genetics, etc…

Format and feed presentation.

Feed particle size and format are extremely important for gut development. Providing mash feed with optimal feed distribution particles, improves feed consumption, nutrient digestibility, promotes digestive organ development and improved gut health for optimizing performance, therefore.

When feed contains too many fine particles, it negatively affects gizzard and proventriculus development, these organs are important due to their essential role in nutrient utilization and gut health maintenance. (Zaefarian et al., 2016)

Graph 4. Influence of feed format and presentation on digestive organs relative weight (g/100g of body weight) in layers. Ege et al., 2019.

Gizzard development is key. A well-developed gizzard, besides reducing feed particle size entering the duodenum, acts as a barrier for microbiota due to pH reduction.


Probiotics are viable microorganisms able to promote a beneficial effect on birds’ gut heath. Mechanisms of actuation include improvement on intestinal microbiota balance, source of energy through short fatty acids (SCFA’s), reducing the capacity of pathogens to adhere to the intestinal epithelium by competitive exclusion and improving enterocyte’s tight junctions.


Prebiotics are characterized by their capacity to modify (in a beneficial way) the composition of intestinal microbiota exerting a positive effect on gut health. They’re different oligosaccharides, including fructooligosaccharides (FOS), galactooligosaccharides (GOS) and mannooligosaccharides (MOS), .whose main feature is that they are able to reach the distal part of intestinal tract where they can be used as a substrate by beneficial bacteria like bifidobacterial or acidolactic bacteria (Ricke, 2018).

Graph 6. Effect of prebiotic on hens challenged with Salmonella Enteritidis. Murate et al.,, 2015.


Is defined as the combination of prebiotics and prebiotics where the latter selectively enhances probiotic growth thereby showing a synergic effect.

Organic acids.

Organic acids are additives that, besides being effective reducing or controlling microbiological contamination of the feed (Theron y Rykers Lues, 2011), have been proven to exert beneficial effects on gut health and performance. Their effectiveness depends on the kind of acid (pka and molecular weight), concentration, dosage and pH. At lower levels of pH, a higher concentration of non-dissociated form can be expected.

Their inclusion in hens and pullets’ diets stimulate endogenous enzyme activity, improves mineral solubility and can have an antibacterial effect therefore supporting gut intestinal integrity.

Water can be also a source of contamination due to the potential presence of microorganisms. Inclusion of organic acids is a common practice to control their proliferation and improve performance.


Phytobiotics represent natural plant derived compounds associated with antimicrobial, antifungal, antiparasitic, anti-inflammatories, antioxidant and immunomodulatory properties.

Essential oils are within this group. Antioxidant properties of essential oils will influence the immune response however there can be a high variability of results from different essential oils.

Exogenous enzymes

For many years the inclusion of exogenous enzymes in hen’s diets has been standard practice. Xylanases, β-glucanases, mannanases, lipases, proteases, phytases to name a few, or indeed, combinations of exogenous enzymes are often supplemented dependant on raw material availability and quality in order to reduce the impact of antinutritional factors, such as NSP’s, phytic acid or proteases inhibitors. As they may affect the process of digestion and the absorption of nutrients with the potential of compromising gut health.


The avian intestinal tract is a series of organs that performs two important functions: digestion and supporting the immune system. The microbiota present at the digestive tract is key to maintaining gut health and, therefore, productivity. Factors like management, diet, etc. influence the presence and proliferation of pathogens that pose a risk factor that may trigger infections. Any action should be addressed that will help maintain the balance between commensal and pathogenic flora.

Within strategies, prevention will be our best ally. From a nutritional standpoint there are a variety of additives that have proven, through different mechanisms, their potential to support intestinal ecosystem maintenance and immune function.