Carbohydrases and proteases can increase the nutrient digestibility in plant-derived feedstuffs.
Enhanced nutrient digestibility does not necessarily translate to improvement in performance.
More research is needed to support the claimed effects of enzyme supplementation on growth performance.
Swine diets are composed mostly of plant-based ingredients. Nutrients contained in these feedstuffs need to be broken down by the pig into simpler forms that will be used to support maintenance, growth, and reproduction. This poses a problem, because, unlike ruminants, pigs do not have the ability to efficiently digest plant components that have relatively high fiber content. Pigs lack specific enzymes needed to break down fiber. Supplementing swine diets with exogenous carbohydrate-degrading enzymes that break down fiber has become increasingly popular to potentially improve availability of nutrients from ingredients with high fiber content.
What are enzymes?
Enzymes are proteins that accelerate chemical reactions that would proceed at a very slow rate under normal conditions. Enzymes are used as feed additives in swine nutrition to improve digestion and utilization of nutrients. On the basis of this premise, enzyme supplementation may potentially result in better growth performance and less nutrients being excreted as waste. Most enzymes, especially those used as feed additives, are characterized by names with the suffix “ase” (eg, xylanase). Carbohydrate-degrading enzymes or carbohydrases act on starches and indigestible cell-wall components. Carbohydrases commonly used in swine diets include β-glucanase and xylanase, as well as α-amylase and cellulase. Proteases are enzymes that break down protein molecules into simpler forms that can be absorbed in the gut. They can also act on protein-based anti-nutritional factors (ANFs) to neutralize their effects.
What are the enzyme modes of action?
Plant-based ingredients contain varying amounts of ANFs, such as non-starch polysaccharides in cereal grains and trypsin inhibitors in soybean meal. Their anti-nutritive effect, caused by their resistance to the pig’s digestive enzymes, may interfere with digestion and negatively affect performance. The proposed modes of action and roles of exogenous enzymes1 include the following:
- Degrading feed components resistant to endogenous enzymes;
- Inactivating ANFs to increase the efficacy of endogenous enzymes;
- Supplementing endogenous enzymes that are otherwise present in insufficient amounts within the animal (eg, proteases in young pigs).
Enzymes are highly specific and therefore must match the specific substrates present in feedstuffs included in the diets. It is, therefore, necessary to carefully evaluate the active enzymes present in a product and the level of enzyme activity present. If possible, feedstuffs must be analyzed for the types of substrates present to better match the enzyme product.
What are the expected benefits from using enzymes?
While carbohydrases and proteases have been used in poultry quite successfully, this has not been the case in pigs. A number of studies2-5 have shown that exogenous enzymes can improve the digestibility of nutrients in feedstuffs commonly used in pig diets, though the positive increases in digestibility have not consistently translated into improvements in growth performance, especially in diets based on corn and soybean meal.6-9 One of the supposed effects of enzymes is the increased availability of energy from fibrous plant materials. Increasing the availability of energy from feed ingredients should improve feed efficiency. Published scientific data,6,7,10-13 on the other hand, show mixed results and are inconclusive. One theory accounting for the differences in digestibility data and production responses is that the enzymes increase the digestibility of feed ingredients in the large intestine, while most of the absorption of nutrients occurs in the small intestine. Thus, the absence of a beneficial effect of enzyme supplementation in pigs, or a limited beneficial effect, may be the result of increases in digestibility occurring at a location in the gastrointestinal tract where the pigs are unable to use the increased energy to influence growth rate or feed efficiency.
Use of enzymes in diets containing dried distillers grains with solubles
Dried distillers grains with solubles (DDGS) have relatively higher fiber content than do traditional feed ingredients like corn and soybean meal. As more DDGS are used in swine diets, there also has been an increasing interest in adding enzymes in such diets to improve their energy value. However, data from recent studies 5,8,14 have not shown significant improvements in growth performance of pigs fed enzyme-supplemented diets. Even at very high levels of DDGS (60%), addition of commercial enzymes did not result in performance improvements.
Choosing the appropriate enzyme product depends on the chemical composition of the diet, which is determined by the feedstuffs included in the diet. For example, diets based on wheat will probably respond more to added xylanase, while barley will respond more to β-glucanase. It is very important to ask suppliers for published data on the enzymes actually present in the commercial product, and not just their research data. This will be helpful in evaluating the cost benefit of using the product. In other parts of the world, enzyme products may be available from unreliable traders. Procure products only from companies with proven track records and that are well-known in the industry.
Do multi-enzyme combinations (cocktails) work better than single-enzyme preparations?
As enzymes are highly specific, a combination of different enzymes may work better than a single enzyme. However, several studies4,6,14,15 have not been able to support this assumption. Still, the use of multi-enzyme products is widely practiced in other countries, where a variety of byproducts can be found in a single diet and where, theoretically, more significant response to enzymes may be seen.
Like other proteins, enzymes are broken down in the digestive tract. No metabolites are absorbed or residues excreted through the feces, so no withdrawal period is required.
Carbohydrate-degrading enzymes, proteases, and their combination have been shown to improve nutrient digestibility of feedstuffs in pigs.2,10,16 However, there is still a lack of scientific data that would support commercial enzyme use in pig diets, as research data have failed to consistently show benefits in performance.5-7,12,14 Therefore, enzyme cost relative to the benefits achieved is not justifiable at this time for regular inclusion in swine diets.
11. Nyachoti CM, Arntfield SD, Guenter W, Cenkowski S, Opapeju FO. Effect of micronized pea and enzyme supplementation on nutrient utilization and manure output in growing pigs. J Anim Sci. 2006;84:2150–2156.
12. Grandhi RR. Effect of dietary ideal amino acid ratios, and supplemental carbohydrase in hulless-barley-based diets on pig performance and nitrogen excretion in manure. Can J Anim Sci. 2001;81:125–132.
13. Mavromichalis I, Hancock JD, Senne BW, Gugle TL, Kennedy GA, Hines RH, Wyatt, CL. Enzyme supplementation and particle size of wheat in diets for nursery and finishing pigs. J Anim Sci. 2000;78:3086–3095.
*14. Jacela JY, Dritz SS, Tokach MD, DeRouchey JM, Goodband RD, Nelssen JL, Prusa KJ. Effects of high levels of distillers dried grains with solubles (DDGS) and enzymes on growth performance and carcass traits of grow-finish pigs [abstract]. Abstract #163. J Anim Sci. 2009;87E-Suppl3. Available at: www.asas.org/abstracts/2009sectional/Supplement_3-42.pdf. Accessed 31 August 2009.
15. Officer DI. Effect of multienzyme supplements on the growth-performance of piglets during the pre-weaning and post-weaning periods. Anim Feed Sci Technol. 1995;56:55–65.
16. Diebold G, Mosenthin R, Piepho HP, Sauer WC. Effect of supplementation of xylanase and phospholipase to a wheat-based diet for weanling pigs on nutrient digestibility and concentrations of microbial metabolites in ileal digesta and feces. J Anim Sci. 2004;82:2647–2656.