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Resilient microbiota and performance

What means a resilient microbiota: a bacterial ecosystem that is able to support external challenges such as dietary and environmental issues, vaccinations, antibiotic replacements...

 

Webinar
87'

Resilient microbiota and performance

  • Prof Ducatelle; Prof Rychlik
Forum
Your questions / Our answers

When you mentioned the metabolite (hypoxanthine) you explained about its degradation and the production of H2O2 useful to kill pathogens. But would that oxidant also be harmful for the normal cells?

Richard Ducatelle:

Xanthine oxidoreductase is expressed on the outer surface of the membrane of the epithelial cells, so the H2O2 is produced outside the cells, thus reducing bacterial load in the dense mucus layer. The same probiotic strain also produces niacin, which is taken up by the epithelial cells and acts as an anti-oxidant.

 

Should we better focus on the individual farm situation to define relevant solutions to help manage microbiota?

Richard Ducatelle:

Farm to farm differences are enormous indeed. Soon the time will come that 16S sequencing will be a management tool to follow up the situation on a given farm with respect to microbiota of the flocks. Interpretation of these data still is a challenge today

Ivan Rychlik:

This is apparently possible but, after all, impossible. There are so many farms with so many minor differences in production technologies that at the very end it is impossible to prepare an extra programme for each farm. Moreover, conditions even in the same farm may change in time. In terms of microbiota we therefore try to compare microbiota of chickens kept under extreme production conditions, those from standard intensive production with those from organic farming and identify microbiota members which are always present. Such true core chicken gut microbiota then represents candidates which can be used universally since these are chicken adapted, irrespective of genetic background, feed composition or environmental conditions.

 

Why not to use the litter as a vector of developing the right microbiota?

Richard Ducatelle:

Litter probably can be an ideal vector for the right microbiota, provided the flock was carrying the right microbiota and pathogens were absent. In countries where built-up litter is used for several rounds, that may be the advantage, but it is a gamble, especially with respect to Salmonella.  

Ivan Rychlik:

Technically this is possible, despite this I would be careful. First, the litter will be always of slightly different composition, quality and therefore efficacy. Secondly, it is even difficult to define litter. What is litter? How old the litter is? Remember that gut microbiota are mostly strict anaerobes and these will gradually loose viability if exposed to the air. Only spore-forming bacteria will reliably survive while non-spore forming gut microbiota members will die out within 24-48 hour long exposure of litter to the air. We will then end up in the same situation as in the presence - spore-forming Firmicutes-Clostridiales-Ruminococcaceae or Lachnospiraceae will persist in the form of spores and will colonise chickens from the litter but non-spore forming Gram negative Bacteroidetes will not.

 

What is the impact of fresh or reused litter on the development of a resilient microbiota?

Ivan Rychlik:

This is a similar question as previous one. I would add that especially use of fresh litter should be critically considered. There are some bacterial species which can be controlled by adult hens but environment of the caecum of 1-day-old chicks is permissive for their multiplication. Megamonas is one example, Campylobacter is another. We have repeatedly observed that using caecal contents from a donor hen with Campylobacter abundance around 0.1 % of total microbiota for inoculation of newly hatched chicks results in rapid multiplication of Campylobacter in the caeca of recipient chicks and one week after chick inoculation, Campylobacter can reach upto 10 % of total microbiota in the caecum. Some problems can be solved by the use of litter but others might be created.

 

There is positive effect of fibres on gut health but they also dilute feeds. How should we formulate feeds taking into account microbiota parameters, gut health and how?

Richard Ducatelle:

Broilers don't need a large amount of fiber, but the fiber fraction of the feed need to have the right composition so as to support the healthy (caecal) microbiota. Most of the time, the amount of fiber in the ingredients is sufficient, so difficult to steer on its own. Fiber in the ingredients often is insufficiently accessible for the immature microbiota. this can be compensated by adding enzymes or adding a small amount of additional partly degraded fiber (prebiotic).

 

What about dysbiosis and performance? Are we not always on the edge? Should we better manage such a dysbiosis status in highly productive animals?

Richard Ducatelle:

The digestive system appears to be able to cope with a certain level of dysbiosis. Farm animals in general are pushed for maximum performance and broilers in particular have been selected for high feed intake. This inherently holds the risk of dysbiosis. Poor performing animals and slow growing animals have a lower risk of developing dysbiosis and intestinal health issues. So indeed in the high performing production systems the animals are continuously on the edge. In the future there will be a need for rapid alert systems based on quantitative biomarkers warning the farmer when the risk increases for the birds to tip over the edge and develop 'wet litter'

Ivan Rychlik:

Certain degree of dysbiosis might be of positive effect on certain parameters of performance. Use of antibiotics to prevent excessive multiplication of gut microbiota, i.e. to keep dysbiosis in the early days of life, results in better performance in terms of body weight increases or feed conversion ratio. However, this results in other issues such as increasing antibiotic resistance and costs which human population. These have to be “paid” outside chicken production and such costs may dominate over the short-term profit in animal production. Next, once you deliberately induce dysbiosis, you have to realise that you are going out of balance and you have to be much careful on feed quality or zoohygienic conditions. Salmonella will always colonise dysbiotic chickens more efficiently than those with developed and complex microbiota. Dysbiotic animals will be always more sensitive to new challenges, challenges which would be tolerated by animals with resilient microbiota.

 

How the future withdrawal of therapeutic antibiotics will affect the gut microbiota?

Ivan Rychlik:

Data from the field show that mortality in the broiler flocks treated with antibiotics during first days of life is 1-2 % lower than in the flocks raised without antibiotics. I am sure that novel strategies will appear when the preventive administration of antibiotics is further restricted.

 

To get an equilibrium at the microbiota level, is it relevant to try to remove all pathogens, or is there any acceptable level of pathogens needed to make an equilibrium with commensal/good bacteria?

Richard Ducatelle:

A well-balanced microbiota is able to suppress certain pathogens, as we have shown in case of Salmonella. Salmonella can sense butyrate and swithes off its virulence mechanisms for colonization and invasion of epithelial cells. Supporting the beneficial microbiota thus may help to control certain pathogens.

Ivan Rychlik:

I do not think that all (opportunistic) pathogens have to be eliminated from the chicken intestinal tract by commensal microbiota members since pathogenicity is also a function of bacterial load.

 

What do we expect from the intestinal microbiota: more nutrients available for the host, signal molecules to enhance absorption capacities, better resistance to challenges?

Richard Ducatelle:

In broilers, the contribution of the microbiota to overall energy intake of the bird is limited, but can become critically important during episodes of starvation, thus protecting the birds from fatal hypoglycemia. Signalling is much more important, as the signals derived from the metabolites of the microbiota are sensed by the host through specialized receptors. these signals are converted into an endocrine response of the host allowing a shift form inflammatory phenotype to tolerant phenotype with ensuying improved absorption and digestion of nutrients.

Ivan Rychlik:

Concerning nutrients, one has to keep in mind that microbiota can metabolise many substrates present in the feed which can be and should be resorbed by the chicken host. This is one side. Opposite approach is that microbiota can degrade and metabolise ingredients present in the feed which are difficult or even impossible for digestion by chicken host. Such ingredients are then metabolised by gut microbiota mostly into organic acids which can be resorbed and utilised by the host. So there is certainly certain competition for nutrients between microbiota and host but microbiota can produce metabolites available to the host. Moreover, some of these metabolites may exhibit signaling properties. But remember that gut microbiota are also prokaryotes, prokaryotes expressing the same molecular patterns like bacteria considered as pathogens. Microbiota may there induce low level of innate immune response thus keeping intestinal tract activated and ready for challenges with real pathogens.

 

How commensal microbiota can adapt to pathogens (Salmonella, Campylobacter) to minimize their effects on birds but being still an issue for consumers?

Richard Ducatelle:

A well-balanced microbiota is able to suppress certain pathogens, as we have shown in case of Salmonella. Salmonella can sense butyrate and switches off its virulence mechanisms for colonization and invasion of epithelial cells. Supporting the beneficial microbiota can lower Salmonella colonization levels by several logs. However, the stress caused by harvesting the birds and transporting them to the slaughterhouse can rapidly increase the level of Salmonella because Salmonella can sense the host stress hormones

Ivan Rychlik:

Our experience is that commensal microbiota increase chicken resistance to Salmonella challenge. However, Campylobacter is completely different story and whatever probiotic mixture we have tested so far, these did not increase chicken resistance to Campylobacter colonization.

 

Can we have a resilient microbiota under different feeding regimes? can we consider that a resilient microbiota could be ‘universal’ (implementation of a unique mature microbiota whatever feeding regimes, environmental conditions….)

Ivan Rychlik:

Feed composition will certainly affect the composition of gut microbiota. But if we consider commercial production with globally recommended feed composition in terms of available energy, protein, carbohydrate, fat or mineral content, extreme differences in gut microbiota composition as a function of feed are less than more likely. This, of course, does not exclude certain differences in microbiota composition under controlled experimental conditions, between two groups of chickens provided two different feed formula. My response is also supported by reports from different part of world describing similar principles of chicken gut microbiota despite the fact that each group use a feed from local supplier who in Australia, China, Czech Republic, USA or Brasil certainly use slightly different feed ingredients.

 

Can we have a resilient microbiota under different environment conditions: hot climates?

Richard Ducatelle:          

It is more difficult to have a resilient microbiota under hot climate conditions because heat stress is an oxidative stress, thus creates an inflammatory phenotype on its own, making birds more susceptible to other challenges.

Ivan Rychlik:

It is likely that microbiota composition in the chickens stressed by hot climate will slightly differ from the microbiota of chickens kept under optimal conditions. But keep in mind that as long as it is possible, chickens will preserve constant temperature, anaerobic conditions and continuous feed supply along their intestinal tract. Hot climate therefore cannot affect microbiota composition directly. The effect of climate is therefore more indirect, when other systems respond to elevated temperature, peristalsis may change, more or less mucins, antimicrobial peptides, bile salts etc. will be released or resorbed from the gut lumen and all of this will consequently affect also microbiota composition.

 

When targeting an optimal gut microbiota, should we include fungi, virus…?

Richard Ducatelle:          

Not much is known about the intestinal virome in birds. Research is still going on but so far the role of the virome does not appear to be as obvious as the role of the microbiome. The same is true for fungi.

Ivan Rychlik:

This area deserves more attention. Although more based on feeling and indirect experience during different experiments, I believe that the role of prokaryotes dominates over the contribution of fungi or viruses in healthy chickens.