Increasing overall digestibility in pigs to capture the full value of your feed

Although cereals and protein meals contain high levels of valuable nutrients, animals are unable to fully utilize them due to their inaccessibility or limited digestibility. In general, complete feed contains more than 20% indigestible fractions, which are composed of dietary fibers, phytate and nutrients presented in forms not completely available to monogastrics.

1. NDF and AX negatively impact the general digestibility, amino acid absorption, and digestible energy in swine diets

Fibers received great attention in animal nutrition due to their significant positive and negative effects in various arenas, such as behavior, welfare, digestibility and performance. In addition, the use of fiber-rich feeds in swine diets is of primary interest as a way to reduce feed cost and prevent competition between feed and food industries for starch-rich raw material. These fiber-rich feeds were generally considered to have low nutritional value due to the lower digestive energy or amino acid levels compared to concentrated feeds with high starch or protein content (Woyengo et al., 2014). Optimal use of these products is extremely important to ensure sustainable animal production. The effect of high-fiber ingestion has generally been a reduction in pig growth rate. However, the reports obtained have often been contradictory. Fibers consist of a variety of different components, as shown in Figure 1.

The synthesis of internal and published studies has been performed (Figure 2) and it clearly demonstrates the detrimental effect of fiber evaluated as NDF – neutral detergent fiber (part of dietary fibers) – on growing pigs and piglets.

Figure 2: Impact of dietary fibre (neutral detergent fiber; NDF) on Average daily gain (ADG)

This synthesis demonstrates a negative correlation between NDF and performance. It also suggests a more detrimental effect on pigs compared to piglets.

Within NDF, arabinoxylans (AX) are the most represented NSPs in the main cereals and by-products commonly used in swine feed. Digestible energy and amino acid digestibility are highly correlated with the level of arabinoxylans present in feed: the higher the level of arabinoxylans, the lower the energy and amino acid digestibility (Figure 3). Arabinoxylans are anti-nutritional factors for swine; they decrease fecal digestibility by 1% and ileal digestibility by 0,6% for every 10 g/kg of total AX. These values suggested a rather similar effect of ANF on amino acid and digestibility.

Figure 3: Impact of arabinoxylans on gross energy and amino acid digestibility

2. Taking full advantage of enzymatic action

Indeed, taking full advantage of enzymatic action requires a good understanding of the content and structure of indigestible fractions and anti-nutritional factors present in feed ingredients. It is the first step in being able to predict optimal enzyme effect. Enzymes used in feed should match the specific substrates found. Factors to be considered when choosing an enzyme solution to achieve optimal results may include:

• Dietary NSP concentration and quality (such as arabinoxylans and its soluble and insoluble fraction);
• Phytate level.

Enzymes are very specific to their substrates. That’s why the same family or dosage can have different levels of activity, and thus different performances in pigs depending on the dietary context. When choosing an enzyme solution, a full understanding of all the diet substrates and anti-nutritional factors present in the feed will help make the best choice. Effect variability is associated with specific enzyme activity and properties. As a consequence, special attention should be paid to the combination of multiple enzymes and debranching enzymes in addition to their kinetic and pH profiles, favoring of course a multienzyme solution that is active across a wide pH range with broad substrate specificity. A fribrinolytic enzyme might also be applied for phytase.

3. Using feedase to increase overall feed digestibility

There are many complex interactions between enzymes, substrates and the gut. As suggested in the previous section, the detrimental effect of fiber might be considered the same for all nutrients. Consequently, fiber hydrolysis increases the digestibility of all nutrients in the same way.

A combination of several exogenous enzymes should be approached as a unique enzyme solution – together they attack the anti-nutritional factors found in each combination of raw materials, releasing nutrients from them. This principle is known as the Feedase approach. Understanding these collective effects, as well as how gut health has been influenced, is the best way to precisely predict performance.

To demonstrate the synergistic effect of different enzymes on the performance of growing pigs, a multi-carbohydrase was added to highly concentrated phytase, creating a multi-carbohydrase plus phytase complex (MCPC – Rovabio® Advance Phy, Adisseo). The study, carried out at South Dakota State University, evaluated the effect of MPCP on the performance of grower-finisher pigs (Jerez-Bogota et al., 2020).

A total of 276 Lance-Large White female × Duroc male hybrid pigs were part of the trial, carried out at Swine Education and Research Facility, South Dakota State University (Brookings, SD) in the USA. The experiment followed a complete randomized design, with 5 dietary treatments, 9 replicates and 6 or 7 pigs per replicate. Five typical American corn-wheat-soybean meal-based diets were formulated as follows:

• PC: NE and nutrients specification based on NRC 2012 recommendations
• NC : -5% NE, -5% digAA, -0.134% unit digP, -0.119% unit Ca
• NC + Rovabio® Advance Phy

Over the whole growth period (34 to 120 kg body weight), pigs fed either of the un-supplemented negative control diets had poorer performance than the positive control. The addition of the MCPC, to both negative control diets, resulted in better performance. Figure 4 shows that the gain to feed ratio reached at least the same level as the positive control. This data demonstrates that the addition of MCPC was able to recover the performance lost when feeding lower specification diets. The reduction in nutrient levels saved €20/t of feed, compared to the positive control. This equates to a saving of €4.50 per pig.

The Feedase approach improves the precision of formulation recommendations for the whole enzyme complex added to feed. It also contributes to a reduction in the use of phosphorus and nitrogen resources, decreasing nutrient waste, whilst at the same time achieving excellent animal performance.

Figure 4: The addition of Rovabio® Advance Phy improved overall gain to feed ratio in pigs

a, b, c – column with different superscripts differ significantly (P < 0.05)

The improved performance could mostly be explained by an increase in the apparent total tract digestibility (ATTD) of dry matter, gross energy, crude protein and phosphorus (Figure 5). This means that, the NE and dig AA can both be lowered by 5%, together with a reduction of 0.134 % unit of dig. P, and 0.114 % unit of Ca, in pig diets – without any negative effects on growth performance or bone ash (Figure 6).

Figure 5: Effect of dietary treatment on ATTD of dry matter, gross energy, crude protein and phosphorus

Figure 6: Effect of dietary treatment on bone (femur) ash

Conclusion

Product names and availability may vary by region, please contact your local Adisseo representative for more information.