An Examination of β-glucanase

β-glucanase was first used in barley-based rations in Europe. Barley contains a large amount of soluble Non Starch Polysaccharides (NSP) in the form of β-glucans and arabinoxylans. These β-glucans result in poor nutrient absorption through large increases in gut viscosity. Thus, as early as the 1980s, β-glucanase enzymes began to be supplemented in barley-based rations to alleviate some of these detrimental effects.

Based on the β-glucan content of corn and soybean meal (see below), it would appear that there was little potential for improvement through β-glucanase supplementation in corn and soy-based poultry rations. However, this is somewhat misleading, as some β-glucanases function as cellulases.

Bach-Knudsen, Knud Erik, 1997. Carbohydrate and lignin content of plant materials used in animal feeding. Anim. Feed Sci. Tech. 67: 319 - 338.

Cellulose, one of the primary components of plant cell walls, represents a large portion of the NSP content of most cereal grains and oilseeds (see above). For instance, cellulose represents approximately 28% of the total NSP present in soybean meal and approximately 22% of the NSP present in corn. Cellulose consists of long chains of D-glucose subunits, linked by β-1, 4 linkages. For these β-1, 4 linkages to be separated, the activity of endo-1, 4-β-glucanase is required. As poultry do not produce this enzyme endogenously, it must be supplied in the ration.

It should be pointed out that it is very unlikely that cellulose can be degraded to its glucose subunits by an NSP degrading enzyme given the short transit time in the digestive tract of poultry. Rather, potential for improvements in digestibility exists through the ability of endo-1, 4-β-glucanase to elicit structural changes in the cell walls of grains and oilseeds, which could allow the bird’s endogenous enzymes better access to nutrients. 

Why Use Xylanase?

As mentioned in my previous email, this email will discuss the importance of xylanase enzymes.

Some of the Non starch polysaccharides (NSPs) typically present in grains and oilseeds are arabinoxylans and heteroxylans. Hence, there is potential for increasing dietary energy as well as improving digestion by supplementing xylanases in poultry diets.

Xylanase supplementation is often associated with diets based on wheat. This is largely because xylanases were first used with wheat-based poultry rations in Europe, as well as the fact that arabinoxylans make up a large portion of the NSP present in wheat.

Bach-Knudsen, Knud Erik, 1997. Carbohydrate and lignin content of plant materials used in animal feeding. Anim. Feed Sci. Tech. 67: 319 - 338.

Xylanases, however, also have potential benefits in corn and soybean meal based rations. Corn typically contains about 9.9% NSP on a dry matter basis, of which approximately 6% is made up of arabionoxylans (see above).

Soybean meal contains approximately 22% NSP, of which about 9% is made up of arabinoxylans.

Thus, the potential exists for xylanases to liberate energy from the NSP contained in corn and soybean meal-based rations.

One important consideration to remember regarding all enzymes is that they react with a specific substrate, and xylanases are no exception. As such, xylanases differ, and cannot be compared quantitatively from product to product. For instance, below it can be seen that an arabinoxylan typically requires four specific xylanase activities to be broken down to a simple sugar.

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For different arabinoxylans, however (such as the highly branched arabinoxylans found in corn), a different sequence of xylanase activity is required to effectively break down the NSP.

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Therefore, enzyme products which contain multiple xylanase activities should have higher potential for improving digestibility over a broader range of feedstuffs.

As arabinoxylans represent a large portion of the NSP present in most cereal grains and oilseeds, it is evident why so many commercial carbohydrase enzymes seek to express xylanase activity.


In our next Rovabio Mail, we will examine the enzyme β-glucanase.

Why Use Enzymes?

Recently, many carbohydrase or non starch polysaccharide-degrading (NSP) enzymes have become available commercially for use in poultry rations. Over 50% of poultry feed now contains supplemental NSP enzymes. NSP enzymes have clearly reached the “tipping point” of acceptability.

These products exist in several forms:

• Pure enzyme products which exhibit only one specific enzyme activity
• Blends of pure enzymes commonly referred to as “cocktails”
• Multi-enzymes (i.e., enzyme products produced from a single organism which expresses multiple enzyme activities)

Monogastric animals, such as poultry, possess endogenous enzymes which aid in the breakdown of different nutrients for digestion and absorption. For instance, poultry possesses protease which helps to break down protein, lipase which helps to digest fat, and amylase which helps to digest starch.

However, monogastrics have no endogenous enzymes capable of digesting non-starch polysaccharides. NSPs are complex carbohydrate structures which make up part of the cell walls of cereal grains and oilseeds. The two tables below show the amount of NSPs in various grains and oilseeds.

Bach-Knudsen, Knud Erik, 1997. Carbohydrate and lignin content of plant materials used in animal feeding. Anim. Feed Sci. Tech. 67: 319 - 338.

NSPs exert negative effects on digestion beyond their inability to be digested. NSPs exist in both soluble and insoluble forms. The soluble NSPs negatively impact digestion by forming viscous solutions in the gut, which can also result in issues such as wet droppings. The insoluble NSPs are thought to impede digestion by simply creating physical barriers which limit the access of endogenous enzymes to carbohydrates, fats and proteins.

As monogastrics possess no endogenous enzymes for NSP digestion, they must be provided in the diet. Feeding carbohydrase enzymes allows for improvements in digestibility, allowing poultry to utilize more of the energy and amino acids present in grains and oilseeds.

I will be writing a series of emails on various carbohydrase enzyme activities and why they are needed. In the next email, I’ll examine xylanases and how they work to break down a portion of the NSP found in grains like corn.