Published on June 8, 2020

By Mike Bedford, AB Vista Research Director

For many years the consensus among feed manufacturers, producers and nutritionists was that fibre had a negative impact on livestock; therefore, diets were formulated without it. However, more recently it has become increasingly apparent that fibre plays a vital role in the development of the gut microbiota – the trillions of cells, including bacteria, viruses, and fungi in an animal’s digestive system – since it is a key substrate for bacterial growth.

This means that – as the total dietary fibre content of monogastric diets tends to be higher than people expect when measuring only crude fibre – there is a huge opportunity for nutritionists to harness the ‘treasure trove’ of potential laying within.

As we further unravel the complexities of fibre, we also improve the provision of nutrients to the gut microbiota for better performance. This is of course especially significant when antibiotics are no longer a central part of diets.

The future for fibre in monogastric nutrition
It seems we may be on the verge of entering an exciting new era: one where nutritionists simultaneously consider nutrition for the microbiota – or the ‘second brain’ – in addition to overall animal nutrition. Our improved understanding of dietary fibre in the diet and the impact of enzymes and oligosaccharide provision in the hindgut offers an exciting future for animal nutrition.

The emerging ‘stimbiotic’ concept involves products which stimulate the development of a fibre fermentable microbiome. This concept involves including a low concentration of products that are used as a signal or kickstarter, driving the microbiome to ferment the fibre that is already present in the gut.

This is a different approach to prebiotics. In that situation the product is added in high concentrations to be used as a substrate for hindgut fermentation. Prebiotics also resist digestion affecting bowel habits.

Key modes of action of fibre-degrading enzymes
When looking at the mode of action of fibre-degrading enzymes, viscosity remains a problem for wheat and barley, it plays only a very small part of the response observed when using fibre-degrading enzymes in corn-soy diets.

In terms of the cell wall mechanism, when we look at the volume of enzyme and how much time is needed to break down cell walls completely, it is far in excess of what we feed the animal in real-life conditions. As a result, we don’t believe the cell wall mechanism plays much of a role, even in a corn-soy diet.

In contrast, the prebiotic mechanism is emerging as the strongest for corn-soy diets – and we feel that the ‘prebiotic’ theory should in fact more accurately be referred to as a ‘signalling’ mechanism.

Reading the signals
The term ‘signalling’ refers to how oligosaccharides generated by fibre-degrading enzymes ’signal’ to bacteria in the gut, stimulating them to produce their own xylanases.

This process has a beneficial effect on fibre fermentation, both in poultry and swine. This theory suggests that xylanase affects the microbiome, changing the concentrations of short chain fatty acids (SCFAs) in the large intestine in such a way that these SCFAs are feeding back to the stomach, telling it to slow down – resulting in a significant improvement in terms of protein digestion.

Enzyme selection and feed formulation

Central to the signalling hypothesis is the theory that an enzyme which can produce xylo-oligosaccharides will eventually improve the ability of the microbiome to digest the arabinoxylan fraction of the diet. This gives far greater benefits in terms of energy and signalling back to the stomach – thus, we believe that feeding the right xylanase that can produce the right signals will give you the best response in commercial feed today.

It is important for feed manufacturers, producers and nutritionists to examine the complex nature of fibre and best harness its intrinsic value in order to formulate a diet that optimises animal performance – and business profitability. Only then can they unlock the ‘treasure trove’ hidden within.

To find out more about the way fibre-degrading enzymes work, watch our video in I explain the shift in thinking related to the three hypotheses commonly used to explain the mode of action of fibre-degrading enzymes – dispelling the cell wall theory as a principal mode of action.