Effect of condensed tannins in Dorycnium rectum on its nutritive value and on the development of sheep parasite larvae


  • G.C. Waghorn
  • A.L. Molan




Sheep and laboratory trials have been undertaken to evaluate the potential value of Dorycnium rectum (Erect Dorycnium) for controlling gastrointestinal parasites. This perennial shrub grows to 3-4 m and can be cut or used as a browse forage. The leaves contain condensed tannin (CT) at about 20% of the dry matter (DM). Sheep were fed D. rectum to determine its digestibility and the effects of CT upon digestion. DM digestibility was 59.6% and increased to 63.6% (P<0.05) when the effects of CT were removed, with comparable values of 23.6% and 73.6% for nitrogen (N) digestibility. Condensed tannin was extracted from D. rectum to evaluate its in vitro effects on egg hatching and larval development of the gastrointestinal parasites Trichostrongylus colubriformis and Ostertagia circumcincta. Very low concentrations (200 μg/ml) reduced egg hatching and virtually halted maturation to the infective third larval (L3) stage. Although the CT in D. rectum reduced its nutritive value for sheep when fed as a sole diet, the inhibition of larval development in vitro suggests a possible role for disrupting the cycle of reinfection in grazing sheep. Keywords: condensed tannins, digestibility, Dorycnium rectum, intestinal parasites, sheep







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