Enzymes and gut health

The following article has been published in the July/August issue of Feed Compounder. This was produced by Dr Augustine Owusu-Asiedu and Dr Leon Broom, based on research carried out by Anpario.


Enzymes to combat problem feed compounds


Feed enzyme development, which was primarily focussed on poultry in the late 1980's and early 1990's, has resulted in the majority of broiler feed globally being supplemented with some form of enzyme. Initial work focussed on improving the digestibility of barley, rye and wheat-based poultry diets in Europe, as these feed ingredients contained the highest levels of non-starch polysaccharide (NSP) compounds responsible for reduced digestion and increased incidence of wet litter (Bedford and Morgan, 1996). Initial research showed that there are two types of NSP, insoluble and soluble, and that soluble NSP (ß-glucans and arabinoxylans in cereals) was responsible for the development of highly viscous digesta (Choct and Annison, 1992). Such gut conditions limits endogenous enzyme direct contact with feed particles, as NSPs are not broken down by the bird's natural secretions (Bedford and Classen, 1992; 1993). Even though it is considered a 'low viscosity' grain, NSP in corn and rice can still be a barrier to digestion, as it encapsulates nutrients within their structure, thereby, reducing enzyme access to substrate. In young birds, with reduced capacity for digestion (Sklan, 2004), adding NSP degrading enzymes are especially important to ensure adequate release of energy and amino acids for growth and early nutritional experiences are known to be important in attaining future growth performance targets (Noy and Sklan, 1998).


An increasing need for appropriate enzyme supplementation

The removal of animal-based proteins from European poultry diets in the 1990's, after the advent of Bovine Spongiform Encephalopathy (BSE) saw a major rise in the use of plant-based protein supplement such as soybean meal and peas to balance ration formulations. This highlighted the requirement for adding protease and NSP enzyme combinations to broiler diets to maintain digestion, as a great deal of variability in nutritional quality has been identified in these plant-based protein supplements. In the last decade, more by-products have become available with sources such as biofuel production or local plant protein like rice. Appropriate blends and dose levels of feed enzymes have become increasingly important to maintain growth efficiency as well as minimising faecal output of potential environmental contaminants. Table 1 shows the relative levels of NSP in commonly used poultry feedstuffs.



Table 1. NSP levels in feed raw materials commonly used in poultry diets


Poor digestion and gut health


Correct and efficient digestion is essential for achieving performance goals and ensuring profitable poultry production. Higher levels of NSP from feed materials have been shown to have a direct impact in reducing digestibility of nutrients (Annison and Choct, 1994; Figure 1). Approximate 5% drop in digestion of starch and protein and 15% reduction in fat digestion can have a major impact not only on the availability of these nutrients for maintenance and growth in the birds but can also disrupt how and where the nutrients are utilised in the gut.


Figure 1. Impact of dietary NSP (arabinoxylan) on digestibility of nutrients (Annison and Choct, 1994).


Digestion should be completed in the upper part of the intestines as this is the region where nutrient absorption is most efficient due to the absorptive villi being at maximum density and most numerous. The remaining digesta moving down the gut into the caecum should only contain indigestible elements such as fibre, which can be fermented by hind gut microflora. This then produces beneficial vitamins and energy in the form of volatile fatty acids in monogastrics, which are important for gut health, for example, butyrate has been linked with promoting gut wall cell function.


However, in many cases, complete upper ileal digestion does not occur, due to the presence of NSPs, processing temperatures and variability in the quality of feed materials. For example, during drought conditions, growing cereals typically respond by laying down more NSP in the grain to protect it from dehydration. If feed is over-processed (e.g. excessive heat or high dwell time) then the chemical structure of starch and protein can be changed to make it resistant to digestion from the animal's own endogenous enzyme secretions (Waldron, 1998). This means that intact feed particles can move further down the intestine to the caecum.


The microflora inhabits the caecum in symbiosis with the host animal and is directly affected, in terms of bacterial species and population size, by changes in nutrient availability. For example, protein particles passing into the caecum encourage the proliferation of Clostridium perfringens, which requires high levels of protein as a nutrient source for rapid colonisation. C. perfringens has been implicated in the development of necrotic enteritis in poultry, which is characterised by diarrhoea, poor nutrient uptake and fragile, damaged gut smooth muscle. This disease has been implicated in costing the global poultry industry US$2 billion as estimated in 2000 (World Poultry, 2015). Similarly, α-galactoside carbohydrates found in soybean meal can cause diarrhoea in poultry because they are fermented by undesirable gut bacteria (Choct et al, 2010).


Any imbalances in the caecal microflora can have a detrimental impact on animal performance, due to toxin damage to the gut wall. This inhibits nutrient uptake, reduces VFA and vitamin production and increases diarrhoea, which can cause wet litter and welfare problems, including hock burns and foot pad dermatitis. Not only does undigested feed encourage the proliferation of undesirable and toxic bacteria, it increases the overall bacterial load in the gut, which can overspill from the containment of the caeca, moving further up the digestive tract where bacteria will compete with the host bird for nutrients from digested feed (Collett, 2004).


Feed enzymes decreases undigested nutrient in the hind gut and improves gut health

Feed enzymes have been shown to increase digestion at both an ileal and faecal level in poultry in many research trials. The recent movement to increase the use of by-products, especially plant protein meal, makes the addition of NSP enzymes more important to prevent the movement of intact nutrients to the hind gut (De Keyser et al., 2015). This can prevent utilisation by undesirable bacteria, unbalancing the gut microflora populations which limits host energy and nutrients availability, reducing performance and increasing the chance of diarrhoea. The type of enzyme must be specific to the target substrates which need to be digested. Therefore, matching the enzyme product to the feed type is important. For example, where NSP is the main problem from cereals containing high levels of arabinoxylan and β-glucans, then arabinoxylanases and β-glucanases should be included in the diet. Changes in microbial populations have been reported when suitable enzymes have been included in the gut, as shown by Zhang et al. (2014). This research showed a clear decline in undesirable bacteria, i.e. Salmonella and E.coli, but promotion of Lactobacillus and Bacillus spp. (Figure 2). Other data (unpublished) showed a drop in caecal Clostridia spp., Salmonella spp. and E.coli relative populations, with an increase in Bifidobacter spp. for broiler chickens fed diets supplemented with xylanase enzymes. Amerah et al. (2012) showed that xylanase addition to broiler diets decreased relative abundance of Salmonella spp. from 32.5% down to 15.5%.


Figure 2. Impact of enzyme inclusion level and abundance of various hind gut bacteria.


There are strong links between gut microfloral populations and productive performance in broilers, whereby higher numbers of beneficial bacteria (Figure 3) are related to improvements in weight gain (Khodambashi et al. 2015).


Figure 3. Impact of increasing Lactobacillus level and daily weight gain in broilers.


Such modes of action of enzymes on gut health and efficiency, added to the increases in nutrient digestibility, result in better performance of growing broilers on farm. Trials with by-products have shown increased performance in broilers when NSP specific enzymes, such as Optizyme™ containing a specific combination of xylanase and β-glucanases, were included in the diet. Trials conducted on amino acid digestion and performance using broilers whereby the diet was supplemented with Optizyme (0.2%) and formulated with different levels of rice bran by-product (7.5, 15 and 30%) from 28-49 days of age, showed that the enzyme ameliorated the negative effects of increasing levels of NSP from rice (Attia et al., 2003). In commercial studies carried out in Spain, Belgium and Germany, Optizyme supplementation improved FCR by 6.0, 2.4 and 7.0%, respectively in broilers fed corn-SBM-based diets. In laying hens, fed basal diets containing wheat, SBM and flaxseed-based diet, adding Optizyme improved FCR and egg production by 4.2 and 5.0%, respectively (unpublished).


Enzymes for modern diets


As raw materials for poultry diets continue to compete with human feedstuffs and biofuels, the need for alternatives is increasing, especially if the cost of feed can be maintained at an acceptable level for broiler producers. Numerous novel feedstuffs are put forward every year for poultry diets, most recently being the increase in focus on insect meal. Such by-products need careful characterisation to assess any anti-nutritional factors they may contain, and suitable enzyme combinations and doses require to be added in order to maintain healthy gut, growth and economic performance of the birds. Ensuring optimal digestion in the upper intestinal tract is key to maintaining a correct microflora population in the hind gut and preventing digestive disorders and disease. Feed enzymes, such as Optizyme, have a major role to play in maintaining this status quo.



Amerah A. M., G. Mathis and C. L. Hofacre. (2012). Effect of xylanase and a blend of essential oils on performance and Salmonella colonization of broiler chickens challenged with Salmonella heidelberg. Poultry Science 91: 943–947

Annison, G. and Choct, M. (1993). Enzymes in poultry diets. Proceedings of the 1st Symposium Enzymes In Animal Nutrition, Kartause Ittingen, Switzerland, pp. 61-68.

Annison, G. and Choct, M. (1994). Plant polyscaccharides,- their physiochemical properties and nutritional roles in monogastric animals. In: Biotechnology in the Feed Industry. Eds. K.A.Jacques and T.P Lyons. Nottinghma University Press, Nottingham, UK.

Attia, Y.A., Qota, E.M.A., Aggoor, F.A.M. and Kies, A.K. (2003). Value for rice bran, its maximal utilisationand its upgrading by phytase and other enzymes and diet formulation based on available amino acids in the diet for broilers. Arch. Geflügelk 67(4), 157–166,

Bedford, M.R. amd Morgan, A.J. (1996). The use of enzymes in poultry diets. World's Poultry Sci J 52 (1): 61-68

Bedford, M.R. and Classen, H.L. (1992). Reduction of intestinal viscosity through manipulation of dietary rye and pentosanase concentration is effected through changes in the carbohydrate composition of the intestinal aqueous phase and results in improved growth rate and food conversion efficiency of broiler chicks. Journal of Nutrition 122, 560-569.

Choct, M. (1997). Feed Non-Starch Polysaccharides: Chemical Structures and Nutritional Significance. Feed Milling International June pp.13


Choct, M. and Annison, G. (1992). Anti‐nutritive effect of wheat pentosans in broiler chickens: Roles of viscosity and gut microflora. British Poultry Science 33(4): 821-834


Choct, M., Hughes, R. J., Wang, J., Bedford, M., Morgan, A. J., and Annison, G. (1996) Increased small intestinal fermentation is partly responsible for the anti-nutritive activity of non-starch polysaccharides in chickens. British Poultry Science 37, 609-621.

Choct, M.; Dersjant-Li, Y.; McLeish, J.; Peisker, M (2010). Soy Oligosaccharides and Soluble Non-starch Polysaccharides: A Review of Digestion, Nutritive and Anti-nutritive Effects in Pigs and Poultry Asian-Australasian Journal of Animal Sciences 23, Issue 10, 2010, pp.1386-1398

Collett, S.R. (2004).  Controlling gastrointestinal disease to improve absorbtive membrane integrity and optimize digestion efficiency. In: Interfacing immunity, gut health and performance. Ed. L.A. Tucker and J.A. Taykor-Pickard. Norringham University Press, Nottingham, UK.


De Keyser, K., Kuterna, L., Kaczmarek, S., Rutkowski, A. and Vanderbeke, E. (2016). High dosing NSP enzymes for total protein and digestible amino acid reformulation in a wheat/corn/soybean meal diet in broilers. J Appl Poult Res  doi: 10.3382/japr/pfw006


Jensen et al., 1970

Khodambashi Emami, N., Graystone, E.N. and Broom, L.J. (2015) Organic acid based products promote broiler gut health and performance. Proceedings of the Poultry Science Association Annual Meeting, Kentucky.


Noy, Y. amd Sklan, D. (1998). Metabolic Responses to Early Nutrition. J Appl Poult Res 7 (4): 437-451.


Sklan, D. (2004). Early gut development: the interaction between feed, gut health and immunity. In: Interfacing immunity, gut health and performance. Ed. L.A. Tucker and J.A. Taykor-Pickard. Norringham University Press, Nottingham, UK.

World Poultry (2015)

Waldron, L.A. (1998) The nature of cereal starch & its influence on animal nutrition. Proceedings of the 10th European Poultry Conference, WPSA Jerusalem.

Zhang, G.G., Yang, Z.B., Wang, Y., Yang, W.R. and Zhou, H.J. (2014) Effects of dietary supplementation of multi-enzyme on growth performance, nutrient digestibility, small intestinal digestive enzyme activities, and large intestinal selected microbiota in weanling pigs. Journal of Animal Science 92 (5): 2063-2069