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Tannins for suppression of internal parasites

B. R. Min1, S. P. Hart1, and T. N. Barry2

1E (Kika) de la Garza Institute for Goat Research, Langston University, Langston, OK
2Massey University, Palmerston North, New Zealand

Condensed tannins (CT) have biological effects that may aid in the control of dewormer-resistant internal parasites (IP). It is increasingly evident that control programs based on dewormers are failing to control IP as dewormer resistance has become more prevalent. Thus, alternative IP control strategies are necessary. The CT in forages have potential to be a component of IP control programs. The CT bind proteins and other molecules tightly at near neutral pH, such as occurs in the rumen, with dissociation in the acidic pH of the abomasum, freeing them for digestion. Effects of CT on parasitism can be assessed by grazing ruminants on forages that contain different levels of CT but otherwise are of similar nutritive value. Plant CT may have direct or indirect effects on IP. Direct effects might be mediated through CT-nematode interactions affecting physiological functioning of IP. Recently, in vitro and in vivo studies have shown that CT in several temperate and tropical forages (Hedysarum coronarium, Onobrychis viciifolia, Lotus pedunculatus, L. corniculatus, Lespedeza cuneata, and Quebracho CT) can inhibit infective gut worm larvae of sheep and goats and both gut and lung worms in farmed deer, with effects influenced by both concentration and structure of CT. Furthermore, preliminary research showed a 57% reduction in fecal egg counts (2,722 vs 1,162 eggs/g) and a 74% reduction in total fecal egg output (173 vs 45 x 104 eggs/d) in goats consuming forage Sericea lespedeza (4.6% extractable CT/kg DM) compared with rye/crabgrass. Indirectly, CT can improve protein nutrition by binding to plant proteins in the rumen and preventing microbial degradation, thereby increasing amino acid flow to the duodenum. Several ovine studies have shown that improved protein nutrition reduces parasite infestation. This is assumed to be mediated by enhanced host immunity, which may be especially important with selection for immunity to IP. In conclusion, CT in forages may have potential to aid in the control of IP.


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