Historically, tannins were considered a double-edged sword in poultry diets. Sometimes known for their bitter taste, tannins have traditionally been thought of as anti-nutritional factors in poultry diets. However, growing attention on the development of antimicrobial resistance to antibiotics among consumers has led to increased interest in evaluating alternative ingredients – including tannins – in poultry diets.
Recent research indicates that tannins may help in managing enteric diseases – like coccidiosis and necrotic enteritis – especially in antibiotic free poultry production systems.1,2,3 Yet, there are still many questions regarding tannin use in poultry. As poultry producers consider evaluating tannin-based ingredients, understanding the facts surrounding tannins is key. One thing we know for sure: not all tannins are created equal.
Let’s dive deeper into four key tannin myths to get to know the tannin phytogenic family and understand how to best balance them for maximized, efficient use in poultry production.
Fact: Tannins are a highly diverse group of natural, plant polyphenolic molecules with variable structures and properties. There are two major types of tannins: condensed tannins and hydrolysable tannins. Condensed tannins (CTs), also known as proanthocyanidins, have high molecular weights and are only degraded under strong oxidative or acidic conditions. Hydrolysable tannins (HTs), in contrast, have lower molecular weights and can be hydrolyzed by acids, bases and enzymes. Interestingly, the complex structure of tannins is thought to limit development of bacterial resistance to various tannin molecules.2,3
Fact: The type of tannin and level of tannin present in a feed ingredient is dependent on the plant source. Condensed tannins are commonly found in forages, grains and sorghum.1 Catechins – simple CT structural units – are found in wine, green tea and dark chocolate. While catechins offer antioxidant benefits, high levels of sorghum condensed tannins in poultry diets can weaken protein digestion, inhibit digestive enzymes and reduce feed palatability.3
Hydrolysable tannins, in contrast, are often found in tree wood and gallnuts. Research suggests that bacteria, like Clostridium perfringens, may be unable to develop resistance to HTs.3 Among HTs, two sub-classes exist based on the esterified phenolic acid units: gallotannins – found in tara pods and gallnuts – and ellagitannins which are commonly found in chestnut wood.2 Tannic acid – a gallotannin – is a specific type of hydrolysable tannin. Overall, differences in tannin source will influence the type of tannin and tannin level in a feed ingredient. Manufacturing processes may also impact tannin efficacy in poultry diets.
Fact: Tannin source, tannin structure and dietary tannin content can have a big impact on the nutritive or anti-nutritive properties of the tannin. In general, anti-nutritional effects of tannins are often linked to tannin protein binding which may lower feed intake and decrease digestibility of proteins, carbohydrates and starches.1,3,4 However, many studies showing anti-nutritional effects of tannins utilized diets either with high levels of tannins or diets containing purified condensed tannins from sorghum.2
Alternatively, feeding low levels of hydrolysable tannins has been shown to have beneficial effects on intestinal health and performance of poultry.1,5 For example, the antimicrobial and anti-parasitic effects of tannins are likely related to tannin complexation with microbial enzymes and/or metal ions, like iron, that are required for normal pathogen growth and metabolism.6,7 Thus, the negative binding characteristics of tannins can actually be beneficial when poultry experience pathogen challenges.
Fact: Dietary tannins – when dosed correctly – offer a wide-range of benefits that support optimal gut health and performance of poultry. First, tannins are potent natural antioxidants as well as anti-inflammatory molecules. Second, tannins are astringent, meaning they may help to tighten junctions between intestinal epithelial cells, thereby helping to prevent leaky gut syndrome. Third, tannins have been shown to positively modulate the intestinal microbiota composition and may help to maintain mucosal immunity.2,8 Fourth, tannins offer antimicrobial activities by inhibiting growth of several poultry pathogens such as Campylobacter spp.2, Salmonella spp.2 and Clostridium perfringens.3,9
Despite their historical connotation as anti-nutritive factors, tannin-based feed ingredients can offer poultry producers new solutions to include in their gut health toolbox. Importantly, producers must remember that using tannins in poultry diets is a balancing act. Choosing the right tannin, at the right level and at the right time is crucial to ensure the benefits of tannin-based feed additives are realized.
As a phytogenic and probiotic combination, VANNIX™ C4 serves as a multi-mode of action gut health solution to help minimize the effects of coccidiosis infection as well as reduce the opportunity for secondary bacterial challenges in poultry. Its tannic acid extract (TAE) – a unique hydrolysable tannin – has been shown to inhibit growth of coccidia parasites and reduce intestinal lesions,10 thereby improving intestinal integrity to support optimal performance of poultry.
For more information on how VANNIX™ C4 can support poultry intestinal health, visit kemin.com/vannixc4.
1Mueller-Harvey, I. (2006). Unravelling the conundrum of tannins in animal nutrition and health. J. Sci. Food Agric., 86:2010-2037.
2Redondo, L. M. et al. 2014. Perspectives in the use of tannins as alternative to antimicrobial growth promoter factors in poultry. Frontiers Microbiol. March(5). doi:10.3389/fmicb.2014.00118.
3Hassan, Z. M. et al. 2020. The effects of tannins in monogastric animals with special reference to alternative feed ingredients. Molecules. 25:4680; doi:10.3390/molecules25204680.
4Chung, K. T., et al. 1998. Are tannins a double-edged sword in biology and health? Trends in Food Sci. Tech. 9:168-175.
5Elizondo, A. M. et al. 2010. Effect of tannins on the in vitro growth of Clostridium perfringens. Vet. Microbio. 145:308-314.
6Chung, K. T., et al. 1998. Mechanism of inhibition of tannic acid and related compounds on the growth of intestinal bacteria. Food and Chem. Tox. 36:1053-1060.
7Min, B. R. and S. P. Hart. 2003. Tannins for suppression of internal parasites. J. Anim. Sci. 81(E. Suppl. 2):E102-E109.
8Carrasco, J.M.D. et al. (2018). Tannins and bacitracin differentially modulate gut microbiota of broiler chickens. BioMed Research International, https://doi.org/10.1155/2018/1879168.
9Tosi, G. et al. (2013). Efficacy test of a hydrolysable tannin extract against necrotic enteritis in challenged broiler chickens. Italian Journal of Animal Science, 12:3, DOI: 10.4081/ijas.2013.e62.
10Tonda, R.M. et al. (2018). Effects of tannic acid extract on performance and intestinal health of broiler chickens following coccidiosis vaccination and/or a mixed-species Eimeria challenge. Poult. Sci., 97:3031-3042.
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