The role of condensed tannins towards ovine nematodes and their consequences on host performance

The aim of this thesis was to investigate the two hypotheses that have been put forward to account for the reduction in the level of parasitism observed in sheep that consume condensed tannins. For this purpose in vitro (larval development/ viability assay) and in vivo experiments were performed. In the first two experiments, a model condensed tannin extract (Quebracho) was given as a drench to parasitised sheep to test for the direct effect of condensed tannins towards established adult nematodes. Experiment 1 aimed to provide evidence for a direct anthlemintic effect of condensed tannins towards an established Trichostrongylus colubriformis population. For this purpose the extract was administered to sheep four weeks after their initial infection. There was clear evidence for a direct anthelmintic effect of condensed tannins towards adult T. colubriformis, as demonstrated by reduced faecal egg counts and worm burdens. As T.colubriformis is an intestinal ovine nematode, the susceptibility of other intestinal and abomasal ovine nematodes to condensed tannins was investigated in vitro and in vivo.In vitro larval development/viability assays were performed to test for the effects o f different concentrations of Quebracho extract on pre-parasitic larval stages of one intestinal (Trichostrongylus vitrinus) and two abomasal nematodes (Teladorsagia circumcincta and Haemonchus contortus) (Experiment 2a). The results from these assays showed that larvae from all species were able to develop to infective larvae, irrespectively the concentration of Quebracho extract. Flowever, the viability of infective larvae of all species decreased, as the concentration of condensed tannins increased. Concurrently, Experiment 2b was designed to test whether condensed tannins had a direct anthelmintic effect towards adult populations of either T. circumcincta or H. contortus, or towards a mixed intestinal population of Nematodirus battus and T.colubriformis. Both ovine intestinal species were susceptible to the presence of condensed tannins in the gastrointestinal tract of sheep, as demonstrated from reduced faecal egg counts and worm burdens. On the other hand, neither the fecundity nor the worm burden of abomasal nematodes was affected by the presence of Quebracho extract. The absence of a direct effect against abomasal species could have been due to either speciesspecific differences in susceptibility or organ-specific physico-chemical differences.In Experiments 3 and 4, Quebracho extract was incorporated in both low and high protein diets of parasitised sheep, in order to test for direct and indirect effects of condensed tannins during the establishment and the maintenance of an intestinal nematode infection. Experiment 3 tested whether the consumption of high protein foods supplemented with Quebracho extract fed as an allowance of the liveweight would reduce the level of intestinal parasitism in sheep and consequently improve their performance. Although the level of the parasitic infection, as judged by faecal egg counts and worm burdens, was reduced in sheep offered the foods supplemented with Quebracho extract, their performance was not improved. It was proposed that this could have been due to an anti-nutritional effect of condensed tannin on food digestibility, which sheep were not able to overcome because of the restricted feeding regime. The final experiment of the thesis (Experiment 4) aimed to test whether the ad libitum consumption of either low or high protein foods supplemented with Quebracho extract would reduce the level of intestinal parasitism and achieve improved performance. It was hypothesised that ad libitum intake would enable sheep to eat to the extent required to overcome antinutritional effects of condensed tannins upon digestibility. For this purpose, the Quebracho extract was added in the foods of parasitised sheep at the same level as in experiment 3. The level of parasitism was reduced in sheep offered foods supplemented with Quebracho extract only during the initial establishment of the infection, as indicated by reduced faecal egg counts. Although the digestibility of foods was not affected by the addition of Quebracho extract in the foods, the performance of sheep was not improved. It was proposed that sheep fed ad libitum might require higher concentrations of Quebracho extract in their foods to reduce the level of parasitism, compared to sheep fed restrictedly, as a result of reduced retention time of condensed tannins in the gastrointestinal tract.The outcomes of the above experiments are brought together and the potential applications of condensed tannins as an alternative to control gastrointestinal parasitic infections in sheep are considered in the General Discussion

Conference report : The importance of the gut microbiome and nutrition on health

Open access via CUP agreementPeer reviewedPublisher PD

A basket of options to control worms in organic sheep production systems

The basket of options is not a “one size fits all” approach. It gives farmers the option to select what is best for their circumstances increasing the chances of keeping treatment frequency as low as possible and maintaining drench efficacy as high as possible

Cost-benefit and Acceptance Analysis of Alternative Nematode Control Practices on Organic Dairy Goat Farms: A Case Study in France

This article assesses the costs, benefits, and acceptance of alternative control practices of Gastro-Intestinal Nematodes (GIN) for a typical organic dairy goat farm in France. A participatory Structured-Decision-Making (SDM) framework was used to guide focus group discussions, with an economic farm model and the Rogers and planned behavior theories used within the SDM framework. The study showed that the implementation of alternative GIN control practices can be economically profitable. An increased gross margin of €41 per dairy goat was calculated, which was mainly due to a decrease in the milk withdrawal cost. The simplicity to use or implement the alternative practices and the experience level of the farmers seem to play a positive role in adoption of the alternative practices consisting of more targeted and strategic treatments. The novel information presented in this article contributes towards facilitating the adoption of suitable alternative approaches for parasite control

In vitro anthelmintic effects of bark extracts from Picea abies and Pinus sylvestris against sheep nematodes

Gastrointestinal nematodes (GIN) in sheep are a common cause of reduced animal welfare and performance, and thus, high economical losses. The emerging drug resistance in GIN prompts for new methods in combating infections. Several studies have indicated an anti-parasitic effect of tannin-rich plants when included in the diet. The objective of this study was to assess the potential in vitro anthelmintic efficacy of tannin-rich extracts from bark of common Norwegian trees (spruce and pine) against GIN of sheep

Proteomic approach to identify candidate effector molecules during the in vitro immune exclusion of infective Teladorsagia circumcincta in the abomasum of sheep

International audienceIn the present study we have employed an in vitro organ challenge model to study the post-challenge responses in parasite naïve and immune gastric tissue of sheep, in an attempt to identify the host derived factors involved in immune exclusion of Teladorsagia circumcincta larvae. Proteins present in the epithelial cells and mucus from ovine abomasa following parasite challenge in previously naïve and immune animals were analysed through Matrix Assisted Laser Desorption/Ionization-Time of Flight (MALDI-Tof)-MS and shotgun proteomics. MALDI-ToF analysis of epithelial cell lysates revealed that a number of proteins identified were differentially expressed in naïve and immune cells. These included intelectin and lysozymes, which were present at higher levels in epithelial cell lysates derived from immune samples. A large number of proteins were identified in the mucosal wash from immune tissue which were not present in the mucosal wash of the naïve tissue. Some of these proteins were present in washes of immune tissue prior to the parasite challenge including immunoglobulin A, galectin 14 and 15 and sheep mast cell protease 1. However, other proteins, such as calcium activated chloride channel and intelectin were only detected in the washings from the challenged tissue. The latter may be related to an enhanced mucus release, which may result in entrapment of infective larvae and thus reduced establishment in tissue that has been previously challenged with the parasite. In conclusion, several proteins have been identified which may be involved, either directly or indirectly, in the exclusion and immune elimination of incoming infective larvae. In the present study, the usefulness of the in vitro model has been confirmed, and the global proteomic approach has identified proteins that had not previously been associated with parasite exclusion from abomasal mucosa, such as the calcium activated chloride channel

Newsletter Barkcure No. 2

The second Newsletter for the research project called “Condensed tannins from Norwegian pine and spruce bark - antiparasitic effects and potential commercial exploitation