A good understanding of the content and structure of indigestible fractions and anti-nutritional factors present in feed ingredients is the first step in achieving optimal enzyme function. Enzymes used in feed should match the specific substrates found within it.
Xylanases and arabinofuranosidases:
complementary effects target a broader range of arabinoxylans
An article written in collaboration with INRA (Lafond et al., 2014) showed that due to the specificity of enzymes to one chemical bond, different types of enzymes are required to break-down arabinoxylans. Endoxylanases acts to hydrolyse the xylose backbone, however their activity is frequently hampered by substitution with arabinose residues. To be efficient, endo-1,4- β-xylanases need a long stretch of unsubstituted xyloses, in order to break down the molecular links on the xylan backbone (Lafond et al., 2014). As a consequence, debranching enzyme such as α-L arabinofuranosidases (Abfs) creating smooth xylose backbone for endo-1,4- β-xylanases action. (Figure 1).
Figure 1: Degradation mechanism of arabinoxylans
Depending on the substitutions occurring on the xylose backbone which are linked essentially to the kind of cereals, different Abf are required for the debranching work as seen in the figure 2)
Figure 2: A range of Abfs are required to breakdown all types of xylose substitutions
A lower proportion of arabinoxylans can have also ferulic acids linked to the xylan backbone, these are susceptible to feruloyl esterase, a secondary debranching enzyme that can release feruloic acids. Feruloyl esterase from T. versatilis is able to debranch corn arabinoxylans (Vangsøe, C; PhD thesis , may 2020), releasing phenolic compounds, which can bring beneficial effect as anti-inflammatory, a kind of action that have already been shown to have a positive effect on human gut health.
Antinutritional properties of NSPs and consequences of pig performance parameters
Studying how the composition in NSP and particularly AX are dependent on the ingredients, and how it affects AME and the enzyme effect, (Sun et al., 2019) showed that diets including wheat, wheat bran, and soybean meal contained differences till 69% more NDF and 71% more total AX than the wheat, soybean meal diets. The digestibility of the organic matter was the lowest for the NSP-rich diets. Carbohydrases in feeds allow gross energy digestibility improvement from 0.5% to 2.8% for 60 Kg growing phase swine depending on the substrate amount. The highest improvement was observed in diet having the highest level of AX.
| Nutrients | Diet A | Diet B | Diet C |
|---|---|---|---|
| Dry material, % | 85,4 | 85,4 | 845,4 |
| Crude protein, % | 16,7 | 16,2 | 15,7 |
| Fat, % | 1,5 | 1,8 | 2,1 |
| NDF, % | 11,8 | 15,9 | 20 |
| Soluble AX, g/kg | 15,5 | 20,8 | 26,2 |
| Insoluble AX, g/kg | 53,3 | 72,8 | 92,0 |
Graph 1: Gross energy digestibility is linked with AX content of the diet
That study demonstrated that NSP and AX content in the diets are directly related to the level of metabolization from gross energy to digestible energy, and their correlation with the carbohydrase effect.
It becomes more than important to use a large range of enzyme activities. By having many different enzymes, it increases the probability of getting the correct one to breakdown the different branches of heteroxylans.
Increasing the potential by combining carbohydrase complexes with high doses of phytase
Whatever the dose, carbohydrases and phytases have distinct and complementary effects. Therefore, one type of enzyme cannot substitute the efficiency of a combination, because they act on different substrates and have different impacts – but always improve digestibility. Indeed, the addition of carbohydrase and phytase increase energy availability and other nutrients such as amino acid sand fat (Table 1). As a consequence, in theory, their matrix could be sum.
At the same time, carbohydrases liberate more nutrients and reduce viscosity of the digesta, by breaking down NSPs. Additionally, short polysaccharides, created by the action of carbohydrases, have a prebiotic effect favouring beneficial microbiota.
These three effects cannot be achieved by using a high dose of phytase alone. The primary action of carbohydrases on NSPs further increases phytase efficiency, as the enzyme then has greater access to phytates located inside the cell. When used together, the action of carbohydrases and phytase are significantly increased – there are greater improvements in DE, as well as mineral and nutrient availabilities. If we look at amino acids in particular, the combination of carbohydrases and high levels of phytase has been shown to further improve their digestibility – compared to high levels of phytase alone (Figure 6, Jerez-Bogota et al., 2020 and phytase meta-analysis (internal data)).
Figure 3: Effect on amino acid digestibility of phytase alone or in combination with a multi-carbohydrase complex
Phytase metatanalysis: Data (n=293) were analyzed by variance analysis with publication as Random effect diet (n=13) and amino acids (n=8) as fixed effects and phytase dose as continuous variable
Conclusion
Lots of factors must be considered when choosing an enzyme solution to achieve expected results thus optimal nutrition from the feed.
- Dietary NSP concentration and phytate level, which are the enzyme’s substrates
- Type, kinetic and level of supplemental phytases
- Solubility and dietary concentration of non-phytate P
- Dietary concentration of multivalent cations – for example high dietary calcium affects phytase efficacy
- Endogenous phytase activity in the basal diet
- Type, kinetic and number of supplemental carbohydrases (single xylanase vs complex of carbohydrases with debranching enzymes)
- Presence of different xylanases and different ß-glucanases
- Presence of debranching enzymes
The enzymes are very specific to their substrates, that’s why a same family or dosage can conduct to different level of activity so different performances of the pigs depending on the dietary context. When choosing an enzyme solution, the full understanding of the full diet substates and anti-nutritional factors present in the feed will lead to the best choice.
