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Largest worldwide study of animal gut health now completed

The ‘Study of gut microbiota of laying hens from different production systems’ or simply, the ‘Gut health’ project has recently been completed.  
To our knowledge, this is the most detailed and thorough study of the gut microbiota ever undertaken in any animal species.

This research recognised the importance of gut microbiota in the productivity of layer flocks and provided comprehensive information on the typical baseline composition of gut microbiota in healthy layer hens in cage, barn, and free range production systems. 

The findings of this project can now be used as the basis for future gut health research, for example evaluating gut health interventions and approaches to maximising the egg production period and maintaining egg quality throughout the lay. 

For this project, four commercial egg layer flocks were monitored.  These included: 

  • A free range flock which was reared on the floor from day old 
  • A barn flock which was reared on the floor from day old 
  • A cage flock reared in a cage from day old 
  • A multi-age cage flock reared on the floor from day old 

As well as providing an understanding of the microbiota of commercial layer hens in different environments , the research highlighted some interesting trends in layer gut health.  

Most day-old chicks had no microbiota , which means that microbiota are sourced from the bird’s environment and feed.  It is not something they are born with.   

This presents the opportunity to ‘seed’ the layer gut with beneficial probiotics, prebiotics or feed supplements from an early age. However, more research would be required to understand the most effective probiotics, prebiotics, feed supplements and seeding regime.  

The researchers were able to see how raising a flock on dirt or concrete floor effects their gut health. They found that flocks raised on dirt floors had a greater number of gut pathogens, which increased their risk of infection. The researchers suggested that preference should be given to the pullet rearing on concrete floors, to reduce the risk of gut infection.  

Richness in gut microbiota composition, or having a diverse range of microbes in the gut, is correlated with productivity. This project revealed a lot about how environment effects layer microbiota richness.


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The results

Moved to the shed

Richness in gut microbiota decreased in every flock when they were moved to the production shed. 

Spotty liver disease

Richness in gut microbiota decreased in the free range flock following an episode of Spotty Liver Disease. 

Introducing new flocks

Richness in gut microbiota decreased in the multi age cage flock when a new flock was introduced to the shed.  

Age is a factor

Richness in gut microbiota increased in all flocks with age, except the multi age cage flock. 

Late lay

Richness in gut microbiota stabilised in the free range, barn and single age cage flocks in late lay. 

Free range flocks

Richness in gut microbiota was highest in the free range flock. 

Further research would be needed to understand if the free range environment is generally more conducive to a rich microbiota, or if this was just the case in this project.  

The decrease in microbiota richness when the pullets were moved to their production environment could be linked to increased susceptibility to infection at this time.  

The egg quality of the flocks involved in this project was not measured, however all flocks were well- managed, high production flocks. This means that the profile of microbiota uncovered in this research is representative of the gut microbiota of healthy commercial layer flocks.

As we look for ways to improve egg quality in later lay, future research could explore the relationship between gut health and egg quality and investigate ways to improve egg quality through gut health manipulation.  

To our knowledge, this is also the first study that described the development and distribution of gut microbiota in different segments of the digestive tract of laying hens.

Most of the previous studies were focused on caecal microbiota but this research found that the colon had the most complex microbiota and the small intestine had the least complex microbiotas. These findings point to the colon being an important consideration for future feed supplement related research. 

This project generated a huge amount of data and insight about the flocks studied.  

While the findings do provide a new level of understanding of layer gut health, it is important to remember that similar research on the gut microbiota of layers across the country would be necessary to determine if the trends observed on the four farms included in this study are similar throughout industry.