The effects of condensed tannins supplementation of foods with different protein content on parasitism, food intake and performance of sheep infected with Trichostrongylus colubriformis

Rational Design and Testing of Antibacterial Aloe Vera Hemostatic Hydrogel

Bleeding resulting from surgical procedures or trauma, including gunshot wounds, represents a life-threatening health issue. Therefore, the development of safe, effective, and convenient hemostatic agents is critical in securing the "golden time" to save patients' lives. Plant-derived compounds and plant extracts have been regarded as promising sources of hemostatic agents in previous studies, regulating hemostatic function with low toxicity and minimal side effects within the human body. Aloe vera-based hydrogels, which are characterized by flexible strength and high functionality, have emerged as a promising platform for wound applications due to their unique biocompatibility features. This study provides a comprehensive exploration of the utilization of thickening agents and natural agents such as xanthan gum, carrageenan, Carbomer, and alginate in applying aloe vera-based hydrogels as a hemostatic. Furthermore, it also tests the use of aloe vera-based hydrogels for therapeutic delivery at wound sites through the incorporation of various antimicrobial agents to extend the utility of the hydrogels beyond hemostasis. Our novel applied research utilizes aloe vera-based hydrogel as an antimicrobial hemostatic agent, providing valuable insights for a wide range of applications and highlighting its potential to enhance hemorrhage control in various emergency scenarios.

Administration of spruce bark (Picea abies) extracts in young lambs exhibits anticoccidial effects but reduces milk intake and body weight gain

Background

Eimeria spp. are widespread apicomplexan parasites known to cause coccidiosis in livestock, resulting in reduced animal welfare and productivity, particularly in sheep. The treatment options are limited, and there is an emerging development of resistance against registered pharmaceuticals. Spruce bark is rich in plant secondary metabolites (PSM), such as condensed tannins, which are bioactive compounds previously shown to have antiparasitic activity. Here, we examined the anticoccidial properties of bark extract of Norway spruce (Picea abies) against a field isolate of ovine Eimeria spp. by treating Eimeria-infected pre-ruminant lambs with water-extracted bark daily for 12 days. We hypothesised that the bark extract would reduce the faecal oocyst excretion and, consequently, the severity of diarrhoea.

Results

Oral administration of spruce bark extract significantly reduced the excretion of Eimeria oocysts in milk-fed lambs post treatment till the end of the trial 22 days post infection. This difference in oocyst excretion between the treated and the untreated infected animals increased with time.

Compared to the untreated and the sham-infected control group, the group treated with bark extract had softer faeces and reduced milk intake during the treatment period. After discontinuing the treatment, the treated animals got a more solid and formed faeces compared to that of the untreated control group, and the milk intake increased to the level of the sham-infected, untreated control group. The bark extract treated animals had a lower body weight and a lower mean daily body weight gain throughout the whole duration of the experiment.

Conclusions

Bark extract from Norway spruce showed marked anticoccidial properties by reducing the faecal oocyst count and associated diarrhoea in young lambs. Simultaneously we experienced detrimental effects of the treatment, displayed as reduced feed intake and daily body weight gain. Therefore, we suggest conducting similar studies with lower bark extract dosage to explore the possibilities of a better trade-off to reduce the negative impact while maintaining the antiparasitic effect.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13028-022-00629-y.

Use of agro-industrial by-products containing tannins for the integrated control of gastrointestinal nematodes in ruminants

Previous studies have illustrated that different bioactive legume fodders containing condensed tannins might represent one of the options for integrated sustainable control of gastrointestinal nematodes (GIN) in ruminants, which may help address the worldwide development of resistance to synthetic anthelmintics. More recently, impetus has been given to assess the potential antiparasitic activity of less conventional resources, represented by different agro-industrial by-products (AIBPs). This review presents in vitro and in vivo results obtained with a range of tannin-containing AIBPs of various geographical and botanical origins, namely AIBP of nuts, temperate and tropical barks, carob, coffee and cocoa. They tend to confirm the "proof of concept" for their antiparasitic effects and also for other aspects of ruminant production in an agro-ecological context. Socio-economic aspects of the exploitation of such non-conventional resources are also discussed as potential models of the circular economy, by using waste. The different modes of use of these resources are presented in this review, as well as strengths, weaknesses, opportunities, and threats (SWOT) analyses to illustrate the advantages and limitations of on-farm use.

Quebracho tannins aid in the control of Eimeria spp. and gastrointestinal nematodes in lambs and goat kids

The objective was to examine the effects of supplementary quebracho on control of coccidiosis and gastrointestinal nematodes in lambs and kids. In Exp. 1, naturally infected lambs weaned (87.8 ± 0.4 days of age; day 0) in January (winter) were blocked by sex and randomly assigned (n = 10/treatment) to receive supplement with or without 100 g/lamb of quebracho for 28 days. In Exp. 2, single or twin rearing ewes were randomly assigned into two groups, and naturally infected lambs were fed control (n = 28) or quebracho (100 g/lamb of quebracho tannins in feed; n = 27) between -28 and 21 days (weaning = day 0; 70.8 ± 0.1 days of age). In Exp. 3, weaned doe kids (57.6 ± 2.0 days of age) were randomly assigned to receive alfalfa (Medicago sativa) supplement with (n = 9) or without (n = 8) 50 g/kid quebracho or sericea lespedeza (Lespedeza cuneata) with quebracho (n = 8) for 21 days. Fecal oocyst count (FOC), nematode egg counts (FEC), fecal score, dag score (soiling around rear quarters), and blood packed cell volume (PCV) were determined every 7 days. Data were analyzed as repeated measures using mixed models. In Exp. 1, FOC decreased in quebracho-fed lambs (diet × time, P < 0.001) but FEC was similar between treatments during the feeding period (P = 0.19). Packed cell volume (P = 0.19) and fecal score (P = 0.42) were similar between groups. Quebracho-fed lambs had a greater dag score initially (diet × time, P = 0.02), but were similar by day 42 (P = 0.72). In Exp. 2, FOC remained low (P = 0.02), PCV tended to decrease (P = 0.06), but FEC increased on days 14 and 21 (diet × time; P < 0.001) in quebracho compared with control-fed lambs. Quebracho-fed lambs had lower fecal score (diet × time; P = 0.005) but higher dag score (diet × time; P < 0.001). In Exp. 3, FOC of kids fed quebracho (alfalfa or sericea lespedeza supplement) was lower than control (P < 0.001). Fecal score of kids fed sericea lespedeza compared with alfalfa were lower regardless of quebracho (P = 0.01). There were no differences among treatments for dag, FEC, PCV, or body weight (P> 0.10). Quebracho was effective in reducing FOC but not clinical signs of coccidiosis in both lambs and kids, and may not be highly digestible in lambs as it caused loose stools.

Comparison of the in vitro anthelmintic effects of Acacia nilotica and Acacia raddiana

Gastrointestinal nematodes are a major threat to small ruminant rearing in the Sahel area, where farmers traditionally use bioactive plants to control these worms, including Acacia nilotica and Acacia raddiana. The main aim of this study was to screen the potential anthelmintic properties of aqueous and acetone extracts of leaves of these two plants based on three in vitro assays: (1) the egg hatch inhibition assay (EHA); (2) the larvae exsheathment inhibition assay (LEIA) using Haemonchus contortus as a model; and (3) an adult mortality test (AMT) applied on Caenorhabditis elegans. For the EHA, only A. raddiana was effective with IC₅₀ = 1.58 mg/mL for aqueous extract, and IC₅₀ = 0.58 mg/mL for acetonic extract. For the LEIA, all extracts inhibited the exsheathment of larvae compared to the controls, and the aqueous extract of A. nilotica was more larvicidal with IC₅₀ = 0.195 mg/mL. In general, all responses to the substances were dose-dependent and were significantly different from the control group (p < 0.05). For the AMT, the extracts of the two Acacia species were effective but A. raddiana showed greater efficacy with 100% mortality at 2.5 mg/mL and LC₅₀ = 0.84 mg/mL (acetonic extract). The addition of polyvinyl polypyrrolidone (PVPP) to the extracts suggested that tannins were responsible for blocking egg eclosion and inducing adult mortality but were not responsible for exsheathment inhibition. These results suggest that the leaves of these Acacia species possess ovicidal and larvicidal activities in vitro against H. contortus, and adulticidal effects against C. elegans.

Medicinal plant extracts and plant-derived polyphenols with anthelmintic activity against intestinal nematodes

Covering: 2001 up to the end of 2016Polyphenols comprise a structurally diverse class of natural products. As the development of new anthelmintic drugs against soil-transmitted helminthiases is an urgent need and polyphenols are widely used in the treatment of nematode infections in traditional medicine and modern science, we summarize the state of knowledge in the period of mainly 2001 up to the end of 2016 on plant extracts with known polyphenolic composition and of defined polyphenols, mainly from the classes of condensed and hydrolysable tannins, flavonoids, and phenylpropanoids. The diverse biological activity against different helminths and the underlying mechanisms are reviewed.

Anthelmintic potential of Calotropis procera, Azadirachta indica and Punica granatum against Gastrothylax indicus

Anthelmintic activity of both ethanolic and aqueous extracts of Calotropis procera flowers, Azadirachta indica leaves and Punica granatum fruit peel in comparison with albendazole was evaluated through in vitro studies by the worm motility inhibition assay. Significant anthelmintic effects (p < 0.0005) were observed on live Gastrothylax indicus worm as evident from their mortality at 4 h post exposure to both ethanolic and aqueous extracts. Phytochemical analysis of extracts revealed the presence of phenols, alkaloids, saponins, tannins, flavonoids, steroids and triterpenoids. LC-50 values were determined to be 12.05 mg/ml ± 3.24 and 23.52 mg/ml ± 6.4 for C. procera, 24.37 mg/ml ± 4.11 and 21.02 mg/ml ± 4.6 for A. indica, 18.92 mg/ml ± 4.54 and 24.43 mg/ml ± 6.96 for P. granatum ethanolic and aqueous extracts respectively, whereas it was 29.23 μg/ml ± 4.51 for albendazole. The mean mortality index (MI) was 1.0 and 0.90 for C. procera, 0.90 for A. indica and 0.73 and 0.80 for P. granatum ethanolic and aqueous extracts respectively whereas for albendazole it was 1.0. Percent mean worm motility inhibition (%WMI) was observed to be between 70 and 100 % for different extracts.Various concentrations (5-5000 μg/ml) of all the plant extracts and albendazole were used to detect their cytotoxic effects against HeLa cell line to determine CC-50 by MTT assay. CC-50 values, of all the plant extracts were determined to be >1000 μg/ml and for albendazole it was found to be >10 μM. All the three plants can be potential sources for novel anthelmintics.

Evaluation of biochemical, hematological and parasitological parameters of protein-deficient hamsters infected with Ancylostoma ceylanicum

BACKGROUND

Hookworms infect millions of people worldwide and can cause severe clinical symptoms in their hosts. Prospective cohort studies in Brazil show high rates of hookworm reinfection in malnourished children compared to well-nourished children, despite previous treatment. Additionally, soil-transmitted helminth (STH) infections can worsen the nutritional status of affected populations. Therefore, this study aims to clarify the effects of host malnutrition during Ancylostoma ceylanicum infection and how this infection affects host physiological parameters using a hamster model.

METHODOLOGY/PRINCIPAL FINDINGS

Hamsters were divided into four experimental groups: normal diet or low-protein diet (also referred to as "malnourished") and A. ceylanicum infection or no infection. More severe pathogenesis was observed in the infected malnourished group, as demonstrated by significant decreases in the hemoglobin concentration, erythrocyte number and packed-cell volume compared to the non-infected malnourished group. Greater numbers of adult parasites and eggs were observed in the malnourished group compared to the control group; however, the oviposition rate was lower in the malnourished group. In general, greater values of total lipids were observed in malnourished animals compared to control animals, including lipids excreted in the stool.

CONCLUSIONS

In this work, we have demonstrated that animals fed an isocaloric low-protein diet presented more severe pathogenesis when infected with A. ceylanicum. The increased lipid concentration in the liver and blood is related to the conversion of the excess carbohydrate into fatty acids that increase the concentration of triglycerides in general. Triglycerides were excreted in the feces, indicating that infection associated with malnutrition caused a greater loss of these molecules for this group of animals and confirming the hypothesis that both nutrition and infection are responsible for the malabsorption syndrome. Taken together, the results found in this work confirm the hypothesis that the nutritional condition of the host greatly influences the course of the infection.

Manipulating small ruminant parasite epidemiology through the combination of nutritional strategies

It is increasingly being recognized that non-chemical parasite control strategies may need to be combined to control more effectively gastrointestinal parasitism, result in resilient production systems and reduce reliance on anthelmintics. Here, we consider if and how metabolizable protein (MP) supplementation and anti-parasitic plant secondary metabolites (PSM) may modulate parasite epidemiology through intervention in pasture contamination, development of infection on pasture and larval challenge as target processes. We then propose that combining two or more non-chemical parasite control strategies may have additive effects on host resistance, especially if the individual strategies target different drivers of parasite epidemiology, different processes in the parasite life cycle or different phases of acquired immunity to parasites. This epidemiological framework is used to review recent findings on combining maternal MP supplementation and grazing the PSM-rich bioactive forage chicory as an example of combining nutritional treatments to manipulate parasite epidemiology in a temperate production system. In the absence of available data for combined nutritional strategies in tropical production systems, we make predictions on the consequences of combining such strategies in these systems. We conclude that currently published studies on combining nutritional strategies under temperate conditions show potential to improve additively host resilience and reduce reliance on anthelmintics; however, effects on epidemiology have to date not shown the additive results hypothesized. The framework developed may assist further in evaluating combined (nutritional) strategies to manipulate parasite epidemiology.

In vitro anthelmintic activity of crude extracts of selected medicinal plants against Haemonchus contortus from sheep

Ethanol extracts of 25 plant species were screened for anthelmintic effects against Haemonchus contortus. Ethanol extracts of each plant were used at various concentrations (10, 20 and 30%) to treat 10-day faecal cultures, incubated at 27°C with control cultures which were treated with ethanol for 48 h. Five plants with high efficacies (Ananas comosus, Aloe ferox, Allium sativum, Lespedeza cuneata and Warburgia salutaris) were selected from the first screening for further investigation using ethanol, dichloromethane and water extracts at four concentrations (2.5, 5, 10 and 20%). Ethanol was the most effective solvent. Larval counts decreased with increasing extract concentrations, of which 10 and 20% had similar effects. Lespedeza cuneata caused more than 70% mortality at all concentrations. However, there remains a need to assess in vivo efficacy of these plants.

Interactive effects of protein nutrition, genetic growth potential and Heligmosomoides bakeri infection pressure on resilience and resistance in mice

The ability of animals to cope with an increasing parasite load, in terms of resilience and resistance, may be affected by both nutrient supply and demand. Here, we hypothesized that host nutrition and growth potential interact and influence the ability of mice to cope with different parasite doses. Mice selected for high (ROH) or low (ROL) body weight were fed a low (40 g/kg; LP) or high (230 g/kg; HP) protein diet and infected with 0, 50, 100, 150, 200 or 250 L3 infective Heligmosomoides bakeri larvae. ROH-LP mice grew less at doses of 150 L3 and above, whilst growth of ROH-HP and of ROL mice was not affected by infection pressure. Total worm burdens reached a plateau at doses of 150L3, whilst ROH mice excreted fewer worm eggs than ROL mice. Serum antibodies increased with infection dose and ROH mice were found to have higher parasite-specific IgG1 titres than ROL mice. In contrast, ROL had higher total IgE titres than ROH mice, only on HP diets. The interaction between host nutrition and growth potential appears to differentially affect resilience and resistance in mice. However, the results support the view that parasitism penalises performance in animals selected for higher growth.

Genetic growth potential interacts with nutrition on the ability of mice to cope with Heligmosomoides bakeri infection

Artificial selection for improved productivity may reduce an animal's ability to cope with pathogens. Here, we used Roslin mice, uniquely divergently selected for high (ROH) and low (ROL) body weight, to assess interactive effects of differing growth potential and protein nutrition on host resilience and resistance. In a 2 x 2 x 6 factorial design, ROH and ROL mice were either sham-infected or infected with 250 L(3)Heligmosomoides bakeri and fed diets with 30, 80, 130, 180, 230 and 280 g crude protein per kg. The infected ROL-30 treatment resulted in clinical disease and was discontinued. In the remaining ROL mice, infection and feeding treatments did not affect growth but infection reduced weight gain in ROH-30, ROH-80 and ROH-130 mice. Although infection resulted in temporarily reduced food intake (anorexia) in both mouse lines, mean food intake over the whole experiment was reduced in ROH mice only. ROH mice excreted more worm eggs and had higher worm burdens, with relatively fewer female worms, than ROL mice. However, these resistance traits were not sensitive to dietary protein. These results support the view that selection for high growth may reduce the ability to cope with pathogens, and that improved protein nutrition may to some extent ameliorate this penalty.

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.

The effect of a condensed tannin-containing forage on methane emission by goats

The objective of this study was to compare methane emission by goats consuming the condensed tannin-containing forage sericea lespedeza (Les-pedeza cuneata) or a mixture of crabgrass (Digitaria ischaemum) and Kentucky 31 tall fescue (Festuca arundinacea). Two groups of 12 Angora does (initial average BW = 41.5 +/- 2.7 kg) that previously grazed a pasture of sericea lespedeza or crabgrass/tall fescue for approximately 4 mo were used. After 1 wk of adaptation to metabolism cages, gas exchange was measured for 24 h in an open-circuit respiration calorimetry system with four head boxes. Forage harvested daily from the previously grazed pastures was consumed ad libitum. Crude protein concentration was 10.3 and 13.0%, IVDMD was 64.5 and 75.3%, and the level of condensed tannins was 17.7 and 0.5% for sericea lespedeza and crabgrass/tall fescue, respectively. Dry matter intake (1.11 vs. 0.67 kg/d) and digestible DMI (estimated from IVDMD; 0.71 vs. 0.51 kg/d) were greater (P < 0.01) for sericea lespedeza than for crabgrass/tall fescue. Ruminal ammonia N (3.7 and 9.9 mg/dL; P < 0.001) and plasma urea-N concentrations (16.7 and 20.9 mg/dL; P = 0.07) were lower for sericea lespedeza than for crabgrass/tall fescue. Concentrations of individual and total VFA and the acetate-to-propionate ratio in ruminal fluid did not differ between treatments (P > 0.19). Despite higher DMI by goats fed sericea lespedeza, daily energy expenditure (409 vs. 431 kJ/kg BW(0.75)), heart rate (70 vs. 73 beats/min), and the ratio of energy expenditure to heart rate (5.82 vs. 5.94) did not differ between sericea lespedeza and crabgrass/tall fescue, respectively (P > 0.13). Methane emission expressed as both quantity per day or relative to DMI was lower (P <0.001) for sericea lespedeza than for crabgrass/tall fescue (7.4 vs. 10.6 g/d and 6.9 vs. 16.2 g/kg DMI). Substantial differences between the forages in condensed tannins concentration and methane emission by Angora goats suggest that condensed tannins decreased methane emission.

The effects of changes in nutritional demand on gastrointestinal parasitism in lactating rats

Lactating rats experience a breakdown of immunity to parasites, i.e. they carry larger worm burdens after re-infection compared to their non-lactating counterparts. Feeding high-protein foods to lactating rats results in reduced worm burdens. This could be attributed to changes in gastrointestinal environment or to overcoming effects of nutrient scarcity on host immunity. The latter hypothesis was addressed through a manipulation of nutrient demand by manipulating litter size. Twenty-three rats were immunized prior to mating and re-infected on day 2 of lactation with 1600 infective Nippostrongylus brasiliensis larvae. From parturition onwards, rats received ad libitum low-protein food (100 g crude protein/kg). Litter size were standardised to nine (LS9), six (LS6) or three (LS3) pups, by day 2 of lactation. After a further 10 d, LS9 and LS6 rats carried more worms than LS3 rats. However, feeding treatment did not affect concentrations of mucosal inflammatory cells. Achieved feed intake did not differ consistently between the treatment groups. However, LS9 and LS6 rats lost weight, whilst LS3 rats gained weight during lactation. The results support the view that resistance to N. brasiliensis is sensitive to changes in nutrient demand, and the improved resistance to N. brasiliensis is likely due to effects of overcoming nutrient scarcity on host immunity.

Alternative approaches to control--quo vadit?

The increasing prevalence of anthelmintic resistance has provided a spur for research into 'alternative/novel' approaches to the control of helminthoses that are intended to reduce our reliance upon using chemoprophylaxis. The different approaches either target the parasite population in the host or on pasture, but the goal of all of them is to restrict host parasite contact to levels which minimise the impact of helminths on host welfare and/or performance. Infrapopulation regulation can be achieved through methods that enhance immunity such as optimised nutrition (immunonutrition), genetic selection and vaccination, or by an 'anthelmintic' route using bioactive forages, copper oxide wire particles, or use of targeted selective treatment strategies such as FAMACHA, which reduce the selection pressure for the development of resistance by maintaining a population in refugia. Suprapopulation control can be achieved through grazing management, or by using predacious fungi such as Duddingtonia flagrans. All of these approaches have been developed beyond the proof of concept stage and some are capable of being employed currently. However, some still require knowledge transfer, or commercialisation before they can be tested and widely applied in the field. All of the different approaches present unique challenges to the researchers engaged in developing them, and in comparison to simple prescriptive anthelmintic treatments, their use appears complex and requires some expertise on behalf of the advisor and/or end user. At present, most of our data are derived from trials using single approaches, but it is apparent that we need to move towards integrating some of these technologies which again represents a further challenge to the extension/advisory services. Progress in establishing different approaches requires not only the funding to support their scientific development but also to support the development of computer based models which can be used to highlight deficiencies in our understanding of the control mechanisms and to identify impediments to their introduction. It is inevitable that some of the approaches currently under investigation will fail to become widely applied for a variety of reasons that are not solely financial. These include issues concerned with practicability/applicability, affordability/appropriateness, availability/deliverability and above all, the failure to provide a consistent, reliable effect when used under commercial farming conditions.

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.

In vivoanthelmintic activity ofDorycnium rectumand grape seed extract againstOstertagia(Teladorsagia)circumcinctaandTrichostrongylus colubriformisin sheep

AIM

To assess the in vivo anthelmintic activity of condensed tannins (CT) in the forage species Dorycnium rectum and Medicago sativa, and in an extract from grape (Vitus vinifera) seeds (GSE), against two species of parasite, Teladorsagia (Ostertagia) circumcincta and Trichostrongylus colubriformis, at different stages of their life cycle, in sheep that were parasite-naïve or previously exposed to nematodes.

METHODS

In Trial 1, a factorial treatment structure was used to compare faecal nematode egg counts (FEC) and worm burdens in 40 weaned Romney lambs fed either the CT-containing forage D. rectum (12% dry matter; DM) or M. sativa (lucerne; 0.2% DM). Twenty naïve and 20 previously-exposed lambs were drenched free of parasites then reinfected with known species and numbers of parasites, and housed in pens indoors on a diet of lucerne pellets and chaffed hay. Groups of lambs (n=5 lambs per group) were fed one of the forages over one of two time periods within the parasite's life cycle. Six to nine days after the last feeding of fresh forages, faecal samples were collected for FEC, and all lambs were slaughtered and worm counts conducted. In Trial 2, 12 Suffolk x Romney lambs were surgically implanted with an abomasal cannula and then housed indoors in metabolism crates. After infection with parasites, six lambs were infused continuously over a 14-day period with a commercially available CT GSE (96% DM, made up to 34 g/L in water); the remaining lambs were infused with water. During infusion, samples were collected for egg hatch and larval development assays. After infusion, samples were collected for FEC, and all lambs were slaughtered and worm counts conducted.

RESULTS

In Trial 1, there was a significant (p<0.001) difference in burdens of O. circumcincta between naïve lambs and those previously exposed to parasites, but no other differences were recorded. In Trial 2, lambs infused with GSE had significantly (p<0.05) fewer T. colubriformis at slaughter and significantly (p<0.001) fewer eggs hatched in the egg hatch assay (EHA) than for lambs infused with water. Overall, the differences attributable to GSE were small in magnitude, being an 11% drop in egg hatch, and an 18% drop in numbers of adult T. colubriformis after 14 days of continuous infusion. No other differences were recorded.

CONCLUSION

The results indicate that the in vivo anthelmintic activity of these CT sources is, at best, modest and is unlikely to be of any practical value. Further, these data emphasise that in vitro activity is an unreliable indicator of in vivo efficacy for CT-containing forages and extracts.

Effect of flavan-3-ols on in vitro egg hatching, larval development and viability of infective larvae of Trichostrongylus colubriformis

The effects of flavan-3-ols (the monomer units of condensed tannins (CT)) and their galloyl derivatives on the viability of eggs, the development of first stage (L1) larvae, and the viability of the infective larvae of Trichostrongylus colubriformis were investigated under in vitro conditions. Each of the flavan-3-ol gallates showed some inhibition of egg hatching at 100 microg/ml, and 100% inhibition at 1000 microg/ml, with epigallocatechin gallate being the most effective in the egg hatch (EH) assay. In contrast, none of the flavan-3-ols were able to completely inhibit egg hatching. The flavan-3-ols and galloyl derivatives dose-dependently inhibited the development of infective larvae as assessed by the larval development (LD) assay. A larval migration inhibition (LMI) assay was used to assess the effect of flavan-3-ols and their galloyl derivatives on the motility of the infective third-stage (L3) larvae of T. colubriformis. In general, the flavan-3-ol gallates were more effective than the flavan-3-ols at immobilising the infective larvae as evidenced by their ability to inhibit more (P<0.05-0.01) larvae from passing through the LMI sieves. At 500 microg/ml, epigallocatechin gallate inhibited significantly more (P<0.1) larvae from passing through the sieves than did catechin gallate, epicatechin gallate, or gallocatechin gallate. Comparisons were made between the flavan-3-ols and their galloyl derivatives with the in vitro effects of CT extracts from several forage legumes, which have exhibited effects on parasites in vivo. The forage legumes tested at 200-500 microg/ml reduced the proportion of eggs that hatch, with comparable results to those obtained using the flavan-3-ols. The activities may be influenced by the prodelphinidin: procyanidin (PD:PC) ratios: CT extracts from Lotus pendunculatus and sainfoin have PD:PC ratios of 70:30 and 77:23, respectively, whereas the less active CT extract from Lotus corniculatus has a PD:PC ratio of 27:73. The active CT extracts from forage legumes have epigallocatechin as the dominant flavan-3-ol extender unit, and epigallocatechin is the most active flavan-3-ol in both the EH and LD assays.

Effects of condensed tannins on goats experimentally infected with Haemonchus contortus

Although the use of tanniferous plants or condensed tannins as an alternative to anthelmintics to control gastrointestinal nematodes has been largely documented in sheep, studies remain scarce in goats. The objective of this study was therefore to assess the possible impact of condensed tannins in goats infected with adult Haemonchus contortus. Two groups of cull goats were experimentally infected with 10.000 L3 of H. contortus. After 4 weeks, quebracho extracts, representing 5% of the diet DM, were administered for 8 days to one of the two groups. Goats of the second group remained as controls. One week after the end of quebracho administration, the goats were euthanised. Individual egg excretion and pathophysiological parameters were measured weekly during the study. At the end of the study, worm counts were assessed and histological samples from the abomasa were taken to count the numbers of mucosal mast cells, globule leukocytes and eosinophils. The administration of tannins was associated with a significant decrease in egg excretion, which persisted until the end of experiment. This reduction was not associated with any difference in worm number but with a significant decrease in female fecundity. No significant changes in the mucosal density of the three inflammatory cell types were detected between the two groups. These results indicate that the major consequence of tannin consumption in goats is a reduction in worm fecundity and egg output, which does not seem related to significant changes in the local mucosal response.

Is the allocation of metabolisable protein prioritised to milk production rather than to immune functions in Teladorsagia circumcincta-infected lactating ewes?

It has been suggested that the periparturient breakdown of immunity to parasites has a nutritional basis. Our overall hypothesis is that it results from a prioritised scarce nutrient allocation to reproductive functions (e.g. milk production) rather than to immune functions. We tested this hypothesis by offering five levels of dietary metabolisable protein, ranging from 0.65 to 1.25 times their assumed requirements, for 4 weeks post-parturition to twin-rearing Greyface ewes, experimentally infected with Teladorsagia circumcincta. We hypothesised that the initial increments of metabolisable protein supply would increase milk production without affecting the degree of breakdown of immunity whilst later increments would reduce the degree of breakdown of immunity. The first two increments of metabolisable protein supply indeed increased milk production and did not affect final worm burdens, but in contrast to the expectation, reduced faecal egg counts and total egg output. The last two increments of metabolisable protein supply did not further affect milk production and egg output, but resulted in reduced final worm burdens. Metabolisable protein supply did not affect plasma IgG and IgE antibody against somatic L(3) antigen but the first three increments reduced plasma pepsinogen and plasma IgA antibody. The last increment did not further reduce plasma pepsinogen but increased plasma IgA. Metabolisable protein supply did not systematically affect abomasal mucosal mast cell, globule leukocyte and eosinophil counts. Our results support the view that the priority of scarce metabolisable protein allocation to milk production over immune functions may be gradual rather than absolute. The contrast between effects of metabolisable protein supply on faecal egg count and final worm burden points towards the possibility that if different effector responses regulate fecundity and worm expulsion, then they would differ in their sensitivity towards changes in the degree of nutrient scarcity.