Introduction
Fibre degrading enzymes have been used in pig feed for many years. The use of fibre degrading enzymes was inspired by the application in poultry feed where very positive results were obtained. The content of poultry feed is in many aspects similar to pig diets: Cereals and soybean meal are the main ingredients in a vast majority of the feed used for the categories of animals. What was not clear in the infancy of NSP enzyme application in pig feed was that the mechanism of action in poultry cannot be transferred to pigs. The most important mechanism of action in poultry is the viscosity reducing effect when the water soluble polysaccharides are degraded. It was however, not clear at that time that the viscosity of the digesta in pigs plays a minor role for most pigs maybe with the only exception seen in weaners where the digestive system is not yet developed.

Important characteristics
Since the commercial introduction of NSP enzymes in pig feed and transition into a commodity prices have dropped significantly. This means that the price for supplementing feed with enzymes has been reduced to only a fraction of what it was 10 years ago. Even though the price has dropped to the benefit of the end-user there are some issues where special attention should be drawn:

Heat resistance
Enzymes can easily be de-activated during the pelleting process where they are subject to high temperatures and humid conditions. Therefore it is very important to know the heat resistance characteristics of the product used.  The temperature during the pelleting process can reach higher temperatures than many people expect. Especially if production capacity of the feed mill is pushed to the limit it often seen that the temperature in the pelleting dye will increase. If there are any doubts about remaining enzymatic activity after pelleting then it is a good idea to collect some samples and analyze the activity.

pH optimum
NSP degrading enzymes should preferably have the highest activity at pH values of 7 because the main activity is preferable in the small intestines. Enzymes can have their highest activity at various pH values. Some phytase for example express their highest activities at pH 2 and pH 5.

Single or multi-enzyme applications
Commercial enzyme products always contain a wide range of enzymatic activities originating from the fermentation process. Products holding an EU approval usually contain 1-2 main activities such as β-glucanase or xylanase. It is claimed that products with many different enzymatic activities should be preferred due to varying composition of the carbohydrate fraction in the feedstuffs. If the major fractions of the carbohydrate content is considered the most plausible way of applying NSP degrading enzymes is to use single or double acitivity products. The content of e.g beta-glucan or arabino-xylan are the most abundant NSP carbohydrates in most cereals thus the user will get most value of the application if either beta-glucanase or xylanase or a combination are used.

Catalytic characteritics
The commercial xylanases are basically of type GH 11 or GH 10. The GH 11 are good at solubilising xylans from the cell wall matrix. The GH 10 are good at breaking down solubilised xylans, reducing viscosity. Some of the GH 11 may actually cause an initial increase in viscosity. There are also other GH families but the 11 and 10 are the most frequently studied and best described. Eventually, this means that enzymes of type GH 11 are expected to produce the best results in pigs where digesta viscosity is no issue.

Measuring enzyme activity
As opposed to phytase activity there are no consensus as how to measure NSP-enzymatic activity and which units to use. The different ways enzymatic activities are measured can cause som confusion because the activity in product A cannot be compared with the activity in competitor product B. Nevretheless, it is a good idea to collect samples containing with and without enzymes and agree with the provider of the products to analyse the content.

Feed formulation
The effect of exogenous NSP enzymes is to a large extent determined by feed formulation and whether the enzyme is mixed with ingredients which contain the right subtstrate. A range of other parameters can also have an effect on how efficacious the exogenous enzymes are.

It is expected that the effect of using xylanase is equivalent to the content of arabino-xylans in the diet. The problem is that there is no easy way to determine the content of NSP in cereals. Therefore, the addition of NSP enzymes in many cases serve as an insurance against deviations in feed ingredient quality.
When feed is formulated with the inclusion of NSP enzymes it is expected that the amount of available energy for the pigs will increase. How big this increase will be is very difficult to determine and can vary from 0-10 percent increase. In many trials it is observed that the addition of enzymes can increase the content of energy from nothing to approx. 3 percent.

In order to obtain the best results using NSP degrading enzymes it is important that energy:digestible protein (amino acids) is maintained. If this is not the case the animal cannot utilise the released energy and it will deposited as fat. Therefore, it is strongly advised to ask the provider for information about the anticipated increase in amino acid digestibility otherwise the lack of amino acids should be compensated by adding synthetic amino acids or increase the content of crude protein.