Effects of condensed tannins on goats experimentally infected with Haemonchus contortus

Condensed tannins inhibit house fly (Diptera: Muscidae) development in livestock manure

Reducing chemical use for suppressing internal and external parasites of livestock is essential for protecting environmental health. Although plant condensed tannins are known to suppress gastro-intestinal parasites in small ruminants, no research on the effects of tannins on external arthropod populations such as the house fly, Musca domestica L., have been conducted. We examined the impact of plant material containing condensed tannins on house fly development. Prairie acacia (Acacia angustissima (Mill.), Kuntze variety hirta (Nutt.) B.L. Rob.) herbage, panicled tick-clover (Desmodium paniculatum (L.) DC.) herbage, and quebracho (Shinopsis balansae Engl.) extracts were introduced at rates of 1, 3 or 5% condensed tannins/kg beef cattle, dairy cattle, and goat manure, respectively. In a second experiment, we also introduce purified catechin at 1 or 3% of dairy manure dry matter and measured its impact on house fly development. For the house flies used in these experiments, the following was recorded: percent fly emergence (PFE), average daily gain (ADG), and average fly weight (AFW). No effects (P>0.05) in house fly development were measured in the caprine manure. Prairie acacia (20.9% condensed tannins) had no effect on house flies developing in either bovine manures. Tick clover (4.9% condensed tannins) had a negative effect on all three quantifiable variables of house fly development in the bovine manures, whereas quebracho extract (64.0% condensed tannins) at the 3 and 5% rate reduced fly emergence in beef manure and average daily gain in dairy manure. The application of purified catechin at 3%, but not 1%, reduced fly PFE, ADG, and AFW.

Direct and indirect effects of bioactive tannin-rich tropical and temperate legumes against nematode infections

Parasitic infections with gastrointestinal nematodes (GINs) represent a major pathological threat associated with the outdoor production of various livestock species. Up to now, the control of these parasitic diseases essentially relied on the use of commercial anthelmintic drugs. However, resistance to anthelmintics is nowadays widespread in worm populations. Recent results indicate that bioactive tanniniferous plants represent a valuable option as an alternative to commercial drugs for the control of GINs. The pertinent use of tannin-containing fodders as nutraceuticals supposes a clear understanding of the mode of action against the worms. The objectives of this paper are: (1) to discuss the nature and quantity of the active molecules involved in the anthelmintic activity; and (2) to review and analyze the changes provoked to the various parasitic stages. The possible involvement of some main polyphenols to explain the bioactivity of some tannin-rich plants will be discussed as well as the possible effects on the various nematode stages, relying on data obtained either with the temperate forage, sainfoin (Onobrychis viciifoliae) or with the tropical legume tree (Lysiloma latisiliquum). The information on the mode of action will be related to the potential consequences for better field applications under entirely different environmental and ecological conditions of productions.

Anthelmintic screening of fractions of Elephantorrhiza elephantina root extract against Haemonchus contortus

In the previous work conducted, it was found that the root extract of Elephantorrhiza elephantina (Bruch.) Skeels. exhibited good anthelmintic efficacy against eggs and larvae of Haemonchus contortus. This study was therefore undertaken to screen fractions of the extracts of E. elephantina for their anthelmintic activity against adult H. contortus using a bioactivity-guided assay. The adult worm bioassay was conducted using aqueous, hexane and ethyl acetate fractions of the plant extracts at concentrations of 0.312, 0.625, 1.25, 2.5, 5 and 10 mg/ml in vitro. Albendazole and distilled water were used as positive and negative control, respectively. In vitro treatment of adult worms revealed concentration and time-dependent efficacy of the fractions of E. elephantina. The aqueous and ethyl acetate fractions showed a highly significant (P<0.05) motility inhibition at concentrations of 2.5 mg/ml and above after 6 h of exposure, while the hexane fraction showed a significant (P<0.05) motility inhibition at concentrations of 5 mg/ml and above. After 30 h of exposure, all the fractions showed insignificant (P>0.05) inhibition of motility. The fractions of E. elephantina also showed mortality indexes that were not significantly different to each other, as well as to the commercial drug (albendazole). Overall, the ethyl acetate and the aqueous fractions were found to possess the highest anthelmintic activity. We therefore recommend future studies to further investigate effective dosages of these fractions in vivo, as well as a full investigation into the compounds responsible for the biological activity.

Dose titration of sericea lespedeza leaf meal on Haemonchus contortus infection in lambs and kids

The objective of three experiments was to determine the impact of supplementing sericea lespedeza (Lespedeza cuneata; SL) in three concentrations in a loose or pelleted diet on gastrointestinal nematodes (GIN) in small ruminants. Experiments on lambs were conducted at the USDA, Agricultural Research Service in Booneville, AR (Exp. 1) and at Louisiana State University in Baton Rouge, LA (Exp. 2); an experiment on goat kids occurred at University of Maryland-Eastern Shore (Exp. 3). Exp. 1 used crossbred hair sheep lambs naturally infected with GIN that were randomly allocated to diets containing 0, 25, 50, and 75% SL diets (n=11 or 12/diet). Exp. 2 consisted of Haemonchus contortus-inoculated crossbred wool breed lambs that were blocked by gender and FEC and randomly assigned to 0, 25, 50, or 75% SL diet (n=8/diet). Fecal egg counts (FEC) and blood packed cell volume (PCV) were not influenced by SL supplementation in Exp. 1 and 2. Exp. 3 consisted of naturally GIN infected Boer crossbred goat kids in individual pens. Kids were blocked by FEC and randomly allotted to treatments of 0, 20, 40, or 60% SL with 9-13 goats/diet. The more SL fed, the greater the reduction in FEC (P<0.001). There was an increase in PCV in SL fed goats (P<0.001). Larval speciation at the end of the experiment indicated that feces from control animals produced 43% H. contortus larva while 20, 40 and 60% SL resulted in 39%, 35% and 31% H. contortus larvae, respectively. Feeding dried SL may be less effective in lambs than kids, though concurrent studies must be conducted to confirm this.

Nutritional composition and condensed tannin concentration changes as browse leaves become litter

BACKGROUND

The role of condensed tannins (CT) in ruminant nutrition and health makes changes in leaf litter (LL) after abscission of interest. This study compared the effect of different drying methods of green leaves (GL) with that of natural drying of LL on CT, fibre, crude protein (CP) and phosphorus (P) concentrations in nine Texas browse species. Leaves harvested before autumn shedding were oven-dried (OD) or freeze-dried (FD).

RESULTS

Where different (P < 0.05), extractable CT concentrations were higher while protein- and fibre-bound CT concentrations were lower in GL-FD than in LL. Drying method changed total CT concentration in three species. Where different, fibre fraction concentrations were greater in LL than in GL, regardless of drying method. In some species, CP and P concentrations were lower in LL than in GL, but in five species they did not change (P > 0.05) from GL to LL, with CP concentrations ranging from 63 to 151 g kg(-1) in the latter.

CONCLUSION

Browse LL had high nutritive value and CT concentrations, explaining why browsing ruminants utilise this feed resource. However, changes in nutrient and CT concentrations as leaves become litter in some species mean that information on one is not necessarily applicable to the other.

Goat-nematode interactions: think differently

Goats (caprine) and sheep (ovine) are infected with the same principal gastrointestinal nematode (GIN) species, which provoke similar pathological changes and economic consequences. However, until now, the majority of data on host-parasite interactions have been accumulated from ovine studies. This article aims to emphasize the need for specific caprine studies. It is hypothesized that, owing to divergent evolutionary processes, sheep and goats have developed two different strategies to regulate GIN infections, respectively, based on immune response versus feeding behavior. Generation of additional comparative data should result in a better understanding of the possible trade-offs between these two basic regulatory processes. Goat studies should also help to avoid past errors in the control of GIN species owing to the lack of relevant information.

Effect of a tropical tannin-rich plant Lysiloma latisiliquum on adult populations of Haemonchus contortus in sheep

Bioactive plants with anthelmintic (AH) properties represent a promising alternative solution to chemical treatments. The AH effect of several Mexican tannin-rich (TR) plants has been screened in vitro. The in vivo AH effect of one TR legume, Lysiloma latisiliquum (Tzalam) on nematode larval establishment was confirmed. The present trial aimed at evaluating the direct and indirect effects of L. latisiliquum fodder consumption on adult Haemonchus contortus. Twenty-two parasite-naïve hair sheep lambs were allocated to an infected group (I) (400H. contortus L(3)/kg BW on D0) and a non-infected group (NI). From D0 to D28 post infection (PI), all the lambs were fed a complete diet. On D28, the two groups were sub-divided into four groups. Two control (C) groups maintained on the original basal diet (CI: 6 infected lambs and CNI: 5 non-infected lambs). The two treatment groups (T) received L. latisiliquum fodder ad libitum up to D36 when lambs were humanely slaughtered (TI: 6 infected lambs and TNI: 5 non-infected lambs). From D28 to D36 PI, individual fodder consumption and nematode egg excretion were measured daily. At necropsy, abomasal contents were recovered to obtain worm burdens and measure the female worm length and fecundity. Histological samples were taken from the respective abomasums and small intestines to count mucosal inflammatory cells. An increased consumption of TR fodder was observed in the TI vs. the TNI group (P<0.01). Before L. latisiliquum distribution, faecal egg excretion was similar in TI and CI groups. From D29 PI the TI group showed lower faecal egg counts compared to CI group (P<0.02). Although no differences in worm burdens were observed, worms of the TI group were smaller and, according to their size, contained fewer eggs in utero than worms from the CI group (P<0.05). Only minor differences in mucosal inflammatory cells were observed between groups, indicating that the indirect effect was not evident. Thus, a short-term consumption of L. latisiliquum can modulate directly the biology of adult H. contortus affecting the worm size and female fecundity while the worm burdens were not affected. Infected animals ate more L. latisiliquum fodder than non-infected animals.

Effect of repeated wattle tannin drenches on worm burdens, faecal egg counts and egg hatchability during naturally acquired nematode infections in sheep and goats

In vivo and in vitro experiments were carried out to investigate the effect of repeated wattle tannin (WT) drenches on faecal egg counts (FEC), worm burdens and egg hatchability during a naturally acquired worm infection in sheep and goats. For the in vivo experiment, nematode-infected sheep and goats were orally drenched with WT at a dose of 1.3g and 1.6gWT/kg bodyweight per day for three consecutive days respectively while a control group received a placebo. FEC and other worm infection parameters were monitored regularly. Once a surge in faecal egg profiles was evident the drenching exercise was repeated as explained above. The trials were terminated by humane slaughter of all the animals and estimation of worm burdens recovered from their guts. WT drench did not, significantly, reduce FEC or total worm burdens in goats. However, there was a slight reduction in FEC and a significant reduction in Haemonchus contortus worm burdens in sheep. WT drenches were also associated with increased faecal water and mucus contents. The in vitro work involved the use of an egg hatch assay using faeces from WT-drenched and un-drenched goats. A dose-response experiment whereby goat faeces were spiked with different levels of WT and then cultured for larval count comparisons was also carried out. The presence of WT in culture media significantly (P<0.05) reduced egg hatchability. There was a significant negative regression coefficient (R(2)=0.84; P<0.01) between concentration of WT in culture media and percent hatchability of nematode eggs. It is concluded that although the degree of anthelmintic activity of WT drench was limited, especially in goats, the drench was capable of reducing the hatchability of eggs passed out in faeces.

Antimutagenic and antioxidant activities of quebracho phenolics (Schinopsis balansae) recovered from tannery wastewaters

Quebracho extracts are used in tannery due to their high concentration of phenolics. The Mexican tannery industry uses around 450 kg/m(3) of which, 150 kg/m(3) remains in wastewaters and are discharged in drain pipe systems or rivers. The quebracho phenolics recovered from tannery wastewater (QPTW) was characterized by HPLC. The antimutagenic and antioxidant activities as well as the microbiological quality were evaluated. Total phenolic content of QPTW was 621mg catechin equivalent/g sample. Gallic and protocatechuic acids were the major components characterized by HPLC. QPTW showed an inhibition range on aflatoxin B(1) mutagenicity from 16 to 60% and was dose-dependent. Antioxidant activity (defined as beta-carotene bleaching) of QPTW (64.4%) at a dose of 12.3mg/mL was similar to that of BHT (68.7%) at a dose of 0.33 mg/mL, but lower than Trolox (90.8% at a dose of 2.5mg/mL); meanwhile antiradical activity (measured as reduction of DPPH) (60.8%) was higher than that of BHT (50.8%) and Trolox (34.2%). Quebracho residues were demonstrated to be an outstanding source of phenolic acids and for research and industrial uses.

Effect of the consumption of Lysiloma latisiliquum on the larval establishment of gastrointestinal nematodes in goats

The consumption of tannin-rich (TR) forages has been associated with negative effects against gastrointestinal nematodes and with an improved host resilience. It has been hypothesized that tannins affect the capacity of infective larvae to establish in the mucosae of the host. In this study, we aimed at testing this hypothesis using Lysiloma latisiliquum, a tropical TR tree. The objectives were: (i) to evaluate the effect of the consumption of L. latisiliquum on the establishment of nematode third-stage larvae (L3) in goats; (ii) to define the role of tannins in these effects in vivo by using an inhibitor (polyethylene glycol, PEG); and (iii) to examine a possible indirect effect of tannins on the inflammatory response in the digestive mucosa. Eighteen Criollo goats composed three experimental groups. The control group received fresh leaves of Brosimum alicastrum, a plant with a low level of tannins. Two groups received L. latisiliquum leaves either with (L.L.+PEG) or without (L.L.) daily addition of 25 g PEG. After a 7-day adaptation period, each goat was infected with both Haemonchus contortus and Trichostrongylus colubriformis (3000 L3 per species). The goats were slaughtered 5 days after infection and worm counts and histological analyses were performed. No difference in the voluntary feed intake of foliage was observed between the 3 groups. The consumption of L. latisiliquum significantly reduced the larval establishment of both nematode species compared to the control (P<0.01). For both worm species, the effects were totally alleviated with PEG (L.L.+PEG group), suggesting a major role of tannins in the observed effects. Only minor differences in the mucosal cellular response were observed between the 3 groups. These results confirm that the consumption of TR plants reduces the establishment of nematode larvae in the host and that a direct effect is principally involved.

The effect of dietary sainfoin ( Onobrychis viciifolia) on local cellular responses to Trichostrongylus colubriformis in sheep

The effect of sainfoin (Onobrychis viciifolia) hay consumption on the pathophysiology and local cellular responses of growing lambs during infection with Trichostrongylus colubriformis was investigated. Thirty-two lambs, 16 weeks of age, were allocated to 1 of 4 treatment groups (n=8) that were offered either grass (G) or sainfoin (S) hay while concurrently either infected (+), or not (-) with 12,000 L3 T. colubriformis larvae per week for 6 weeks. Liveweight gains were affected by diet (P=0.002) and reduced by infection (P<0.05). Faecal egg count was reduced in S+compared to G+ from days 35 to 42 (P=0.001); however, total egg output, worm burdens at day 42 and worm fecundity were similar between diets (P>0.05).Feeding sainfoin appeared to enhance immune cell development with tissue eosinophils, mast cells and pan T cells present in greater concentrations in S+ than in G+ animals. However, further studies are required to determine if the enhanced immune cell development is a consequence of a greater nutrient supply or a direct influence of sainfoin metabolites on local inflammatory responses to the gastrointestinal nematode T. colubriformis.

In vitro nematicidal effects of medicinal plants from the Sierra de Huautla, Biosphere Reserve, Morelos, Mexico against Haemonchus contortus infective larvae

Twenty extracts from plants from Sierra de Huautla Biosphere Reserve, Morelos, Mexico were evaluated against Haemonchus contortus infective larvae in an in vitro assay. The plant species evaluated were Bursera copallifera, B. grandifolia, Lippia graveolens, Passiflora mexicana, Prosopis laevigata, Randia echinocarpa and Urtica dioica. The plants were separated into their parts and macerated with different solvents (n-hexane, acetone, ethanol and methanol). An in vitro assay was used to evaluate the anthelmintic activity against unsheathed third stage H. contortus infective larvae. The experiment was carried out in 24-well cell culture plates at room temperature with three replicates per treatment and using a concentration of 20 mg ml- 1. Ten 5 microl aliquots were taken from the corresponding wells and deposited on a slide for microscopical observation at 24, 48, 72 and 96 h post-exposure. The evaluation criteria were based on the average numbers of live and/or dead larvae in the different treatments. Alive and dead larval numbers were statistically analysed through the ANOVA test (P>0.01). The Tukey test was used as a complementary tool to determine which treatment was different from the other treatments (P>0.05). The highest mortality was observed with P. laevigata hexanic extract from stem and leaves combined, which produced 51%, 81% and 86% larval mortality at 24, 48 and 72 h post-exposure, respectively. On the other hand, B. copallifera stem acetonic extract exhibited 18%, 59% and 66% nematicidal activity after 24, 48 and 72 h of exposure, respectively.

Individual administration of three tanniferous forage plants to lambs artificially infected with Haemonchus contortus and Cooperia curticei

We investigated direct anthelmintic effects associated with the feeding of fresh tanniferous forages against established populations of Haemonchus contortus and Cooperia curticei in lambs. Twenty-four parasite naive lambs were inoculated with a single dose of infective larvae of these two parasites 27 days prior to the start of the feeding experiment. Lambs were individually fed with either chicory (Cichorium intybus), birdsfoot trefoil (Lotus corniculatus), sainfoin (Onobrychis viciifolia) or a ryegrass/lucerne mixture (control) for 17 days. Animals where then united to one flock and subjected to control feeding for another 11 days to test the sustainability of potentially lowered egg excretion generated by tanniferous forage feeding. When compared to the control, administration of all tanniferous forages was associated with significant reductions of total daily faecal egg output specific to H. contortus (chicory: 89%; birdsfoot trefoil: 63%; sainfoin: 63%; all tests P<0.05) and a tendency of reduced H. contortus worm burden (chicory: 15%; birdsfoot trefoil: 49% and sainfoin: 35% reduction). Irrespective of the condensed tannin (CT) containing fodder, no anthelmintic effects were found against C. curticei. Cessation of CT-feeding followed by non-CT control feeding did not result in a re-emergence of faecal egg counts based on faecal dry matter (FECDM) in any group, suggesting that egg output reductions are sustainable. The moderate to high concentrations of CTs in birdsfoot trefoil (15.2 g CTs kg(-1) dry matter (DM)) and sainfoin (26.1 g CTs kg(-1) DM) were compatible with the hypothesis that the antiparasitic effect of these forages is caused by their content of CTs. For chicory (3 g CTs kg(-1) DM), however, other secondary metabolites need to be considered. Overall, birdsfoot trefoil and in particular sainfoin seem promising candidates in contributing to an integrated control strategy against H. contortus not only by mitigating parasite related health disturbances of the host but also by a sustained reduction of pasture contamination.

Anthelmintic and nutritional effects of heather supplementation on Cashmere goats grazing perennial ryegrass-white clover pastures1

To investigate anthelmintic and nutritional effects of heather supplementation in goats grazing perennial ryegrass-white clover pastures, 40 dry Cashmere goats were randomly assigned to 4 treatments in a 2 x 2 factorial arrangement: 2 grazing management treatments (supplementation with heather vs. nonsupplementation) and 2 anthelmintic treatments (treatment vs. nontreatment). Goats grazed continuously from May to September 2004. At the end of the grazing period, the number of dead goats due to gastrointestinal parasitism was 1 in the group supplemented with heather and dosed with anthelmintic, 4 in the group that received neither supplementation nor anthelmintic, and 0 in the other 2 groups. For goats that did not receive anthelmintic treatment, the percentage of heather in the diet was negatively correlated with fecal egg count in August (r = -0.59, P < 0.05) and September (r = -0.49, P < 0.1) and positively correlated (r = 0.54, P < 0.05) with BW changes during the grazing season. Therefore, the correlation coefficient between BW change and fecal egg count was negative (r = -0.62, P < 0.05). Rumen ammonia concentrations were always lower in supplemented goats (P < 0.05). However, VFA concentrations were greater in goats consuming heather (58.9 vs. 50.9 mmol/L), which suggests that ruminal fermentation was not adversely affected by consumption of tannins. Heather availability in the vegetation might represent a valuable opportunity and sustainable method to control gastrointestinal nematode infections in a goat production system based on grazing perennial ryegrass-white clover pastures.

Effect of sainfoin (Onobrychis viciifolia) silage and hay on established populations of Haemonchus contortus and Cooperia curticei in lambs

The objective of the study was to examine the effect of dried and ensiled sainfoin (Onobrychis viciifolia) on established populations of Haemonchus contortus (abomasum) and Cooperia curticei (small intestine) in lambs under controlled conditions. Twenty-four parasite naïve lambs were inoculated with a single dose of infective larvae of these parasites 28 days prior to the start of the feeding experiment. Twenty-four days post-infection, 4 days prior to the start of the feeding experiment, animals were allocated to four groups according to egg excretion, live weight and sex. Groups A and B received sainfoin hay and control hay, respectively, for 16 days. Groups C and D were fed on sainfoin silage or control silage for the same period. Feeds were offered ad libitum and on the basis of daily refusals were supplemented with concentrate in order to make them isoproteic and isoenergetic. Individual faecal egg counts on a dry matter basis (FECDM) were performed every 3-4 days and faecal cultures and packed cell volume (PCV) measurements were done weekly. After 16 days of experimental feeding, all animals were slaughtered and adult worm populations were determined. The consumption of conserved sainfoin was associated with a reduction of adult H. contortus (47% in the case of hay, P<0.05; 49% in the case of silage, P=0.075) but had little effect on adult C. curticei. Compared to the controls, H. contortus specific FECDM was reduced by 58% (P<0.01) in the sainfoin hay group and by 48% (P=0.075) in the sainfoin silage group. For both sainfoin feeds FECDM specific to C. curticei were significantly decreased when compared to the control feeds (hay 81% and silage 74%, both tests P<0.001). Our data suggest that different mechanisms were responsible for the reduction in FECDM in response to feeding tanniferous fodder. For H. contortus, the decrease seemed to be due to a nematocidal effect towards adult H. contortus. In contrast for C. curticei, the reduction in FECDM appeared to be a result of a reduced per capita fecundity. For both, hay and silage, an antiparasitic effect could be shown, offering promising perspectives for the use of conserved tanniferous fodder as a complementary control approach against GIN.

AN EXAMINATION OF THE INFRACOMMUNITIES AND COMPONENT COMMUNITIES FROM IMPALA (AEPYCEROS MELAMPUS) IN THE KRUGER NATIONAL PARK, SOUTH AFRICA

The intestinal helminth parasites of the impala from the Kruger National Park, South Africa, were examined to describe the parasite community structure. Demographic variation and the associated differences in behavior were used to further investigate the patterns of community composition. Monte Carlo simulations were performed to test for differences in species richness and mean abundance between the various demographic groups, and nonmetric multidimensional scaling ordination was used to compare community composition. Seventeen species of nematodes, totaling more than 1.3 million worms, were recovered. Males harbored a greater number of nematode species than did females, but adult females were more heavily infected than their male counterparts. Lambs acquired infections early in life, and their parasite community composition rapidly approached that of the older animals. The parasite community in the juvenile and adult males was significantly different from the community of the adult females. These data suggest that social and feeding behavior of the different age-sex classes structure the parasite component community of impala. Additionally, the distinction between common and rare parasites, and their classification in other herbivores, implies complex transmission dynamics that includes extensive species sharing within the Kruger National Park.

Evaluation of some plants used in Turkish folk medicine against parasitic infections for their in vivo anthelmintic activity

Ethanolic and aqueous extracts obtained from nine plant species from seven families selected depending on their use in Turkish folk medicine, including Citrillus lanatus (Thunb.) Matsum. (seed), Jasminum fruticans L. (branches), Juniperus drupacea Labill. (fruits), Juniperus nana L. (fruit and leaves), Juniperus oxcycedrus L (fruit and leaves), Mentha longifolia L. (herba), Pinus nigra ssp. pallasiana (Lamb.) Richt. (fruits), Plantago lanceolata L. (leaves), and Zea mays L. (seed) were evaluated for their in vivo anthelmintic activity. Among the plant extracts studied, both ethanolic and aqueous extracts of Jasminum fruticans, Mentha longifolia and Pinus nigra ssp. pallasiana, the aqueous extracts of Zea mays, the ethanolic extracts of Citrillus lanatus, Juniperus drupacea (fruit), Juniperus oxcycedrus and Plantago lanceolata displayed significant anthelmintic activity against pinworms, Syphacia obvelata and Aspiculuris tetraptera, in mice. Rest of the extracts from plants did not show any remarkable anthelmintic activity. The results were considered significant at p<0.05.

Effect of sericea lespedeza (Lespedeza cuneata) fed as hay, on natural and experimental Haemonchus contortus infections in lambs

Parasitic infection is one of the leading economic constraints in small ruminant production. This problem is exacerbated as the resistance of nematode populations to chemical treatment (anthelmintics) becomes increasingly more common. Condensed tannin (CT) containing plants are being investigated as alternative solutions to address these problems. This investigation was conducted to evaluate the effect of the CT containing forage, Lespedeza cuneata (sericea lespedeza, SL) fed as hay, on Haemonchus contortus infection in sheep. Naturally and experimentally infected lambs were fed either SL or bermudagrass (BG, control) hay for 49 days. All lambs were fed BG hay for an additional 14 days. SL hay effectively reduced (67-98%) fecal egg count (FEC) during the time of feeding for both infection groups. FEC increased in both infection groups after SL feeding was stopped which indicated an effect on fecundity. SL hay feeding also reduced worm numbers, with more of an effect on reducing naturally infected worm burdens (67.2%) than on establishment of incoming larvae (26.1%). SL fed as hay may be more useful to remove existing worms than establishing worms. The decrease in FEC would have the benefit of reduced pasture contamination.

Monomers of condensed tannins affect the larval exsheathment of parasitic nematodes of ruminants

The current control of parasitic nematodes in small ruminants relies on the use of chemical anthelmintics, but the development of resistance requires research in alternatives. Bioactive plants represent one of those solutions. Previous results suggest that plants rich in condensed tannins (CTs) might have direct anthelmintic effects. However, the relationships between the biochemistry of active compounds and the mechanisms of action remain to be elucidated. Therefore, this study examined in vitro the effects of different CT monomers on the exsheathment of infective larvae for two nematode species. Monomers of prodelphinidins were more potent inhibitors of exsheathment than those of procyanidins. More severe inhibition was also found with galloyl derivatives. These results suggest that the number of free hydroxy groups of CT monomers is a key factor in interactions with parasite larvae. Comparison of effects between the two nematodes suggests different susceptibility to monomers depending on species, which might be related to the protein composition of sheaths.

Evaluation of efficacy expectations for novel and non-chemical helminth control strategies in ruminants

The interest in novel methods of controlling helminth infections in ruminants is driven primarily by the development of parasite resistance to currently available anthelmintics. While the purpose of anthelmintics is to achieve high efficacy, i.e. >90% reduction of adult and/or larval parasites in the target host animal, the purpose of novel parasite control methods is rather to assist in maintaining parasite infections below the economic threshold. The ability to maintain parasite levels below the economic threshold is related not only to the efficacy of the control method, but also to the epidemiology of the parasites, climatic conditions, the livestock management program, and integration in a sustainable parasite control program. Because of this fundamental difference, novel parasite control methods need to be evaluated using efficacy criteria different from that adopted for anthelmintics. Although the efficacy of novel parasite control methods may be demonstrated in classic dose-confirmation studies, the impact on livestock production parameters can only be evaluated when tested on-farm. In this paper, the rationale for evaluating novel methods differently from anthelmintics is reviewed, potential performance expectations are presented, and four novel parasite control methods (vaccines, nematophagous fungi, condensed tannins, and immunonutrition) are assessed based on the potential performance criteria.

Use of plants in novel approaches for control of gastrointestinal helminths in livestock with emphasis on small ruminants

Helminth infections are a major cause for reduced productivity in livestock, particularly those owned by the poor worldwide. Phytomedicine has been used for eons by farmers and traditional healers to treat parasitism and improve performance of livestock, and many modern commercial medicines are derived from plants. However, scientific evidence on the anti-parasitic efficacy of most plant products is limited, regardless of their wide ethnoveterinary usage. Scientific validation of the anti-parasitic effects and possible side-effects of plant products in ruminants is necessary prior to their adoption as a novel method for parasite control. A variety of methods has been explored to validate the anthelmintic properties of such plant remedies, both in vivo and in vitro. In vitro assays are useful as pre-screens of activity and are mainly performed with the free-living rather than parasitic stages of nematodes. Concentrations of potentially active substances used in vitro do not always correspond to in vivo bioavailability. Therefore, in vitro assays should always be accompanied by in vivo studies when used to validate the anthelmintic properties of plant remedies. In vivo controlled studies have shown that plant remedies have in most instances resulted in reductions in the level of parasitism much lower than those observed with anthelmintic drugs. Whether it is necessary or not to achieve very high efficacy in order for plant remedies to have a role in the control of parasitism depends on the determination of biologically important levels of reduction of parasitism and it will be required prior to the wide-scale use of plant products for parasite control. Similarly, standardisation of validation studies in reference to the numbers of animals required for in vivo studies to measure direct anthelmintic effects of a plant needs to be established. Although in many cases the active compounds in the herbal remedies have not been fully identified, plant enzymes, such as cysteine proteinases, or secondary metabolites, such as alkaloids, glycosides and tannins have shown dose-dependent anti-parasitic properties. However, as some of the active compounds may also have anti-nutritional effects, such as reduced food intake and performance, it is essential to validate the anti-parasitic effects of plant products in relation to their potential anti-nutritional and other side effects. A concerted effort on isolation, development, and validation of the effects of these herbal remedies will have to be undertaken before their wider acceptance.

The effects of tannin-rich plants on parasitic nematodes in ruminants

Apart from the obvious role of plants in herbivore nutrition, they are also a rich source of bioactive products that can operate either to the benefit or the detriment of grazing animals. Here, we review the available evidence for the potential beneficial effects that plant-derived bioactive substances can have on gastrointestinal parasites. Tannin-rich plants have attracted most attention for their effect on internal nematodes in ruminants. These plants could act through direct antiparasitic activity but might also act indirectly by increasing host resistance. The effects vary with the species of plant, parasite and host. More research is required to understand better the mechanisms of action, and therefore make more pertinent use of these bioactive plants in livestock systems.

Lack of effects of quebracho and sainfoin hay on incoming third-stage larvae of Haemonchus contortus in goats

The effects of tannins on adult populations of Haemonchus contortus, Trichostrongylus colubriformis and Teladorsagia circumcincta in goats are characterised mainly by a decrease in egg excretion without any significant changes in worm number. In contrast, the impact of tannins on T. colubriformis or T. circumcincta third-stage larvae (L3) is associated with a significant reduction in worm establishment. The objective of the present study was to examine the effects of quebracho extract tannins on H. contortus L3. The consequences of consumption of sainfoin hay were also examined. Twenty-one naïve kids were divided into three experimental groups. Group Q received quebracho extract and group S received sainfoin hay from days D3 to D5. Group C remained as an infected control group. All kids received 1500 L3 H. contortus on D0, D1 and D2. On D18, post-infection, the kids were slaughtered and the worm populations compared in the different groups. Compared to the control values, the worm counts decreased, respectively, by 33% and 38% in groups Q and S but the differences were not significant. No differences were found in pathophysiological measurements between the three groups. The results confirm differences in tannin effect according to nematode species but not parasitic stage.

In vitro effects of four tropical plants on the activity and development of the parasitic nematode, Trichostrongylus colubriformis

The in vitro effects of extracts of four tropical plants (Zanthoxylum zanthoxyloides, Newbouldia laevis, Morinda lucida and Carica papaya) on the egg, infective larvae and adult worms of Trichostrongylus colubriformis were screened for potential anthelmintic properties. Significant effects were observed with the four plants on T. colubriformis but they differed depending on the stage of the parasite. Extracts of each plant induced a dose-dependent inhibition of egg hatching. Using a larval inhibition migration test, the effects on the infective larvae were also detected with the four plant extracts. In contrast, for adult worms, the effects were statistically significant only for N. laevis and C. papaya. No significant activity was shown for M. lucida and Z. zanthoxyloides. These in vitro results suggest the presence of some anthelmintic properties associated with these four plants, which are traditionally used by small farmers in western Africa. These effects need to be studied under in vivo conditions.

Effect of bioactive compounds from Sainfoin ( Onobrychis viciifolia Scop.) on the in vitro larval migration of Haemonchus contortus : role of tannins and flavonol glycosides

Anthelmintic bioactivity against gastrointestinal nematodes has been associated with leguminous forages supporting the hypothesis of a role of condensed tannins. However, the possibility that other compounds might also been involved has received less consideration. Using bio-guided fractionation, the current study aimed at characterizing the biochemical nature of the active compounds present in sainfoin (Onobrychis viciifolia ), previously identified as an anthelmintic leguminous forage. The effects of sainfoin extracts were evaluated on 3rd-stage larvae (L3) of Haemonchus contortus by using a larval migration inhibition (LMI) assay. Comparison of extracts obtained with several solvent systems showed that the bioactivity was associated with the 70ratio30 acetone/water extract. Further fractionation of the later allowed the separation of phenolic compounds. By use of a dialysis method, compounds were separated with a molecular weight cut-off of 2000 Da. The in vitro anthelmintic effect of the fraction with condensed tannins was confirmed. In the fraction containing molecules of MW <2000 Da, 3 flavonol glycosides were identified as rutin, nicotiflorin and narcissin. At 1200 mug/ml, each inhibited significantly the migration of larvae. Addition of polyvinyl pyrrolidone (PVPP) to both fractions before incubation restored larval migration. These results confirmed the role of both tannins and flavonol glycosides in the anthelmintic properties of sainfoin.

In vitro effects of four tropical plants on three life-cycle stages of the parasitic nematode, Haemonchus contortus

Alcoholic extracts of four tropical plants (Zanthoxylum zanthoxyloides, Newbouldia laevis, Morinda lucida and Carica papaya) were screened in vitro for potential anti-parasitic effects against eggs, infective larvae and adult Haemonchus contortus. Significant effects were obtained with all four plants but differences were observed depending on the parasitic stage. The effects of the four plant extracts were similar on egg hatching and were dose dependent. In contrast, no dose-response relationship was found for infective larvae and adult worms, although more potent effects were usually observed with the highest concentrations. Using a larval inhibition migration test, extracts of fagara (Z. zanthoxyloides) were found to be less active against Haemonchus infective larvae than were the other plants. N. laevis was found to be highly and rapidly effective against adult worms. Overall, these in vitro results suggest that these four plants, traditionally used by small farmers in Western Africa, do possess anti-parasitic properties. These effects remain to be confirmed through in vivo studies.

Effects of the repeated distribution of sainfoin hay on the resistance and the resilience of goats naturally infected with gastrointestinal nematodes

Due to the high prevalence of anthelmintic resistance in goats, the need to explore novel approaches to control nematodes and to reduce the exclusive reliance on chemotherapy is strongly demanded in this host species. In sheep, several studies have shown that the consumption of tannin-rich legume forages was associated with positive effects on host resilience and resistance to parasite infection. In goats, studies on such interactions between tanniferous plants and nematode infections remain few. The objectives of the current study were to examine under natural conditions the effects of consumption of sainfoin hay by goats on the parasite populations and on host resilience. Eighteen adult cull goats naturally infected with Haemonchus contortus, Teladorsagia circumcincta and Trichostrongylus colubriformis were used in the study. At the start of the assay, the goats were allocated into two groups, balanced according to weight and the levels of egg excretion. The two groups grazed separate pastures for 3 months with similar stocking rates. Goats from group S received each month indoors, for 7 days, sainfoin hay and control goats (group C) received hay of ryegrass. The diets in both groups were made isoenergetic and isoproteic and the refusals measured. Individual parasitological and pathophysiological measurements were performed fortnightly in order to compare host resistance and resilience. At the end of the study, five goats per group were necropsied. The distribution of sainfoin was associated with: (1) a higher consumption of hay; (2) significant, lower levels of nematode egg excretion which was associated with a decrease in worm fertility but no change in worm population; however, the number of intestinal worms was reduced by 50% in group S; (3) a better host resilience. In particular, after 2 months of grazing, two control goats died and half of the remaining animals needed to be treated whereas this was not the case in group S. These differences were related to significant changes in pepsinogen and phosphate values (PCV) but not in pepsinogen and phosphate concentrations. These results demonstrate that a repeated distribution of sainfoin hay to grazing goats might be beneficial in regard of pasture contamination and host resilience. They suggest that administration of sainfoin hay might represent a valuable alternative and adjunct to reduce nematode infections in dairy goat flock.