Training bacteria to degrade fibre - Fibre in animal feed

Optimising key ingredients

Tara York and Gilson Gomes, two of our technical experts, address questions about fibre in animal feed and how appropriate nutritional strategies can help producers make the most of their monogastric livestock.

What is fibre in animal feed?

Fibre is a wide-ranging term and encompasses many elements. The makeup of cell wall fibre fractions differ, with some being more digestible than others.

These indigestible fibre fractions are often known as non-starch polysaccharides (NSPs), and a wealth of data exists demonstrating their anti-nutritive properties in poultry diets (Bedford et al., 1991; Bedford and Classen, 1992; Choct and Annison, 1992).

If fibre is anti-nutritive, why is it important?

Published scientific literature contains numerous articles demonstrating the improvements in animal performance observed with the introduction of NSP enzymes. These enzymes break down arabinoxylan into xylo-oligosaccharides (XOS), smaller carbohydrate fragments that are fermented by bacteria. The fermentation of XOS is believed to prompt changes within the microbiome of the gastrointestinal tract, leading to improved animal performance through the production of short-chain fatty acids (SCFAs).

Why has the role of fibre become of more interest?

NSP enzymes have been used in poultry diets for almost 40 years to improve nutrient absorption, with the primary focus on fat, allowing for reduced dietary costs. During this time, our understanding of how they work has evolved.

Past research has suggested that bird performance may be correlated with microflora and the metabolites they produce (Rinttila and Apajalahti, 2013), but as our knowledge of fibre and NSP enzymes has evolved, we are increasingly able to utilize fibre to the benefit of the animal by training the microbiome and igniting its fermentation capabilities.

Fibre has also become a renewed topic of interest in gut health and animal performance as an increasing number of countries have moved toward antibiotic-free production.

What have we learnt about fibre?

A research paper by Bedford (2018) discussed the three principal modes of action suggested for NSP enzymes: viscosity reduction, cell wall destruction and the generation of prebiotics. Within this review, he proposed an adaptation to the prebiotic hypothesis such that NSP enzymes are not producing prebiotics per se but sending signals to the microbiome to develop its fibre degrading ability. As the NSP substrate is broken down into smaller xylo-oligosaccharide fragments, the bacteria can utilize the substrate more effectively, leading to increased caecal fermentation (Masey O’Neil et al., 2014).

Bedford proposed that it may be the fermentation of dietary fibre rather than the oligosaccharides generated by the enzyme that provides the additional energy to the bird and feedback to the gizzard that allows the gizzard to grind more efficiently, resulting in improved nutrient digestion.

It is believed that the generation of XOS leads to a shift in the microbiome toward butyrate-producing bacteria.

Which bacteria are found in poultry intestines?

Although many microbes in the gut of chickens are unknown, approximately 75% come from the species belonging to the phyla Firmicutes. The major species within this phylum belong to the families Ruminococcaceae and Lachnospiraceae, also known as the Clostridium Cluster IV and XIVa, both of which are known to produce butyrate as a fermentation end product (De Maesschalck et al., 2015).

Research has demonstrated that when 26-day-old chickens were fed diets with or without XOS supplementation, an increase in Clostridium Cluster XIVa, along with other bacteria, was found in the ceca, which corresponded with an increase in butyrate production.

What is microbiome signalling?

Although it has been previously suggested that the bird and its microflora are fundamentally linked, our new understanding of fibre breakdown into XOS and the benefits XOS plays in inducing changes within the microbiome of the gastrointestinal tract only supports the significance of this link.

The benefits of XOS reported in the literature on animal performance, however, have been shown when feeding XOS directly as a feed additive and at much higher levels than would be produced by the addition of an NSP enzyme alone (De Maesschalck et al., 2015; Liu et al., 2018).

In the study by De Maesschalck et al., the improvements observed on bird performance when feeding XOS were suggested as a result of stimulating butyrate-producing bacteria through cross feeding lactate and the beneficial effects of butyrate on gastrointestinal function. Microbial populations within the gastrointestinal tract of the animal change over time, with a more specialized fibre fermenting population evolving as the animal ages.

How does the age of the bird impact signalling?

Although the levels of SCFAs are quite low in the intestine and ceca of younger birds (van der Wielen, 2000; Lee et al., 2017), the ability to possibly signal or train the microbiome to become more efficient at degrading fibre and producing SCFAs earlier may provide even greater benefits.

A study (Bedford and Apajalahti, 2018) suggested that the bacteria can be trained to begin fermentation earlier. Researchers in this study asked whether an animal was pre-exposed to an NSP enzyme and if that changes the ability of the caecal microbiome to digest fibre later.

Chickens were fed a control diet with no enzyme, or a diet containing a xylanase enzyme for 35 days. On day 35, birds were sacrificed, and their ceca and microbiome contents were collected. The microbes were then exposed to a variety of inoculants. What they found was that the microbiome from birds pre-exposed to a xylanase enzyme showed not only an improvement in gas production but an increase in the production of butyrate compared to the non-exposed control treatment.

These data suggest that the microbiome was trained and ready to ferment xylan more effectively due to prior exposure.

What is complementary dual action?

For several years, we have been conducting research studies to determine what drives the microbiome’s ability to degrade fibre and whether that knowledge can be optimised to make it even more efficient. This research has led to the development of a novel dual-action product.

Research conducted with this product, now known as Signis, suggests that the butyrate-producing bacteria are able to be signalled to ‘up regulate’ their ability to degrade fibre and begin producing their own enzymes for enhanced fibre degradation, as well as SCFA production.

The dual action of improving fibre solubility and nutrient absorption occurs through a series of events. Additional benefits gained with the production of SCFAs, such as butyrate and its reported benefits on gastrointestinal health (Brons et al., 2002) and the impact of slowing gastric emptying, have led to improvements in animal liability and performance in pigs and poultry.