Interleukin-13 induces paralysis of Haemonchus contortus larvae in vitro.

AIMS: Interleukin-13 (IL-13) is a Th2-associated cytokine that typically induces gut contractility and mucus secretion to eliminate helminth parasites from the digestive tract. Little evidence exists of IL-13's direct effect on Haemonchus contortus larvae (L3) and thus was the objective of this study. METHODS: To test effects of IL-13 on H contortus, L3 were treated with ovine recombinant (r) IL-13 (1 µg/mL); motility and morbidity were assessed. Monocytes isolated from H contortus-resistant St. Croix (STC) and susceptible Suffolk (SUF) sheep were treated with anti-IL-13 blocking antibody to elucidate differences in host immune response. RESULTS: rIL-13 treatment reduced L3 speed (27 µm/s) and distance (7.5 µm) compared to untreated L3 (speed: 94 µm/s; distance: 27 µm) (P < .001). Comparison of larval speed to known paralytic levamisole (LEV) revealed no difference between treatments (rIL13: 23 µm/s; LEV 27 µm/s). Additionally, rIL-13 had no effect on larval morbidity. Blocking IL-13 reduced monocyte-driven larval morbidity (0.13 µmol/L ATP) and increased larval motility (88 µm/s; 27 µm) compared to larvae treated with STC-monocytes alone (0.07 µM ATP; 34 µm/s; 8 µm) (P < .05). CONCLUSIONS: These data indicate IL-13 has a dual capability paralysing L3 and contributing to monocyte-driven larval morbidity, and also indicate breed differences.

Effects of Acacia mearnsii supplementation on nutrition, parasitological, blood parameters and methane emissions in Santa Inês sheep infected with Trichostrongylus colubriformis and Haemonchus contortus.

Gastrointestinal nematodes are a main problem for ruminant production, reducing animal performance and increasing environmental impact per unit of animal product generated. Tannin supplementation may lead to positive results regarding aspects such as parasitic infections and methane (CH4) emissions. Therefore, the objective of this experiment was to evaluate the effects of the condensed tannins (CT) extract made of powdered Acacia mearnsii bark (PAB) on nutrition, parasitic status and CH4 emissions in sheep artificially infected with Trichostrongylus colubriformis and Haemonchus contortus. Twenty 10-month old Santa Inês lambs (24.7 ± 3.14 kg of initial body weight) were used in a 50-day trial. Animals were divided in four treatment groups according to parasitic infection and PAB supplementation: two control groups without infections, one without PAB (C-) (n = 4) and one with PAB (C+) (n = 4); two infected groups, one without PAB (I-) (n = 6) and another receiving PAB (I+) (n = 6). Initially, animals were kept in individual pens where they were fed ad libitum chopped tifton 85 hay (Cynodon spp.) and 210 g/animal/day of concentrate. On the first day of experiment, animals of I- and I+ groups were artificially infected with infective larvae (L3) of T. colubriformis and H. contortus. Lambs were weighed fortnightly to calculate average daily body weight gain (ADG). Blood and faeces samples were also collected in the same moment of weighing for the evaluation of blood parameters and faecal egg count (FEC) respectively. After 40 days of experiment, measurements of CH4 emissions in small chamber system started and following that, apparent total tract digestibility (ATTD) assay was carried out in metabolic cages. In the end of experimental period (50 days), lambs were slaughtered and samples of abomasum and small intestine content were collected for worm count, identification, and eggs/female count. No significant (p > 0.05) treatment effects were verified for ADG, ATTD and worm count. Blood parameters were affected in both infected groups (p < 0.05) from the 28th experimental day onwards, when these animals started to show reduced red blood cells, haemoglobin and packed cell volume when compared to C- and C+. Decreased FEC was verified in I+ when compared to I- and also, H. contortus eggs/female worm for I+ was lower than for I- (p < 0.05). Both infected groups showed higher CH4 emissions than the control groups (p < 0.05). Results highlighted the anthelmintic potential of PAB and indicated methanogenic effect of parasitic nematode infections.

Effects of dietary supplementation with green tea polyphenols on digestion and meat quality in lambs infected with Haemonchus contortus.

Ujumqin sheep are susceptible to infection by the gastrointestinal nematode Haemonchus contortus, which reduces productivity and total meat yield in sheep. Thus, the effects of green tea polyphenol (GTP) supplements (0, 2, 4, or 6g of GTP/kg feed) on dietary nutrient digestibility and meat quality in lambs infected with H. contortus were examined; control lambs were not infected. H. contortus infections did not affect digestion but the apparent digestibilities of nutrients were decreased by dietary 2g of GTP/kg feed supplementation. There was an interaction between treatment and sampling time on plasma total protein, urea nitrogen, and amino acid concentrations. The antioxidant activity and meat color of INFGTP0 lambs decreased. In conclusion, H. contortus infections in lambs decreased meat quality, but appropriate levels of dietary GTP supplementation diminished these negative effects though lower dose of GTP supplement showed negative effects on digestion.

Anthelmintic effect of carob pods and sainfoin hay when fed to lambs after experimental trickle infections with Haemonchus contortus and Trichostrongylus colubriformis.

The aim of the study was to compare the in vivo anthelmintic activity of sainfoin hay (Onobrychis viciifolia) and carob pod meal (Ceratonia siliqua) against gastrointestinal nematodes. Seven days before infection, 64 naive lambs were assigned to four different groups: Group S received sainfoin hay and group CAR was fed with carob pods. The remaining lambs received lucerne hay (Medicago sativa) and were assigned to positive (non-treated, NT) and negative (treated, T) control groups (treatment with albendazole). On day 0, lambs were artificially trickle infected for 6 weeks, with a mixture of infective larvae of Haemonchus contortus and Trichostrongylus colubriformis. Parasitological and pathophysiological parameters were measured repeatedly during the 2-month study. Compared to the NT group, decreases in egg excretion were observed in the CAR and S groups with significant differences only found for sainfoin (p < 0.05). At necropsy, group S showed decreases in the total worm numbers of both nematode species with significant differences for H. contortus. In contrast, no differences were noticed for the CAR group. Compared to the NT group, lower values for fecundity of female H. contortus were found in the S and CAR groups, however differences were non-significant. No differences in body weight gains were found between groups. Consistent results were found showing significantly higher packed cell volume (PCV) values in the T and S groups compared to NT and CAR groups. Overall, these results confirm a positive effect associated with the feeding of lambs with tanniniferous resources on host resilience (PCV values) and against gastrointestinal parasitic nematodes by affecting some biological traits of worm populations (e.g. eggs per gram of faeces and worm numbers). However, the anthelmintic effects differed between the two tannin-containing resources, which might be associated with the quantity and/or quality of secondary metabolites (condensed tannins and/or other polyphenols).

Effect of dietary supplementation with flaxseed oil or vitamin E on sheep experimentally infected with Fasciola hepatica.

The effects of two diets supplemented with flaxseed oil (FO) or vitamin E (VE) were studied in sheep infected with Fasciola hepatica. The control group (CO), not supplemented, had higher weight gain and faecal egg count (P < 0.05) at the end of the study. At necropsy, the number (71.2 ± 26.5) and size of flukes were lower in the FO group (P < 0.01), probably due to the higher levels of white blood cells and lymphocytes (P < 0.01). This group also had higher red blood cell and haematocrit values (P < 0.01). The CO group had more severe hypoproteinaemia and hypoalbuminaemia, due to having the highest fluke burden (123.0 ± 35.2), and also the highest IgG1 titre (P < 0.01). The diet did not affect production or gene expression levels of IFN-γ and IL-4. On the other hand, the supplementation with VE led to a reduction in adult fluke burden (97.7 ± 39.9) and lower lipid oxidation in the liver (P < 0.001).

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.

Dietary modulation of the mucosal immune response to a parasite.

This study investigated the hypothesis that dietary deficiency of readily available carbohydrate (raCHO) modifies the immune response of lambs to the gastrointestinal nematode Trichostrongylus colubriformis. Sixty helminthologically naive Merino lambs were fed throughout the experiment diets containing three levels of raCHO that provided adequate, moderate or low intakes according to recommended standards and were given primary or both primary and secondary infections of T. colubriformis. A further 20 uninfected lambs received the low diet for 9 weeks, after which they were returned to the standard diet. Immune status was assessed by the measurement of plasma and jejunal antibody concentrations and blood and jejunal cell numbers and function. Diets low in carbohydrate resulted in a failure of the lambs to gain weight and decreases in plasma glucose concentration, blood lymphocytes expressing CD8 or Tcrgammadelta, monocytes, eosinophils, platelets and red blood cells, jejunal and plasma antibody concentrations, lymphocyte proliferation to worm antigen and numbers of jejunal CD8(+) and Tcrdeltagamma(+) lymphocytes, eosinophils and CD1b(+) dendritic cells. Thus, a low dietary concentration of raCHOs impaired the constitutive availability of lymphocytes and antigen-presenting cells, and the cellular and humoral immunological responses. A hypothesis is suggested for the mechanism and for the possible wider implications.

Consequences of protein supplementation for anorexia, expression of immunity and plasma leptin concentrations in parasitized ewes of two breeds.

The periparturient relaxation of immunity (PPRI) against parasites in ewes has a nutritional basis. We investigated whether ewes experience a reduction in food intake (anorexia) during PPRI and if the magnitude of anorexia is affected by host production potential and dietary protein supplementation. We also investigated whether nematode infection is linked to plasma leptin concentrations in periparturient ewes. The experiment was a 2 x 2 x 2 factorial design. Two breeds of twin-bearing/lactating ewes (Greyface cross, G (n 32) and Scottish Blackface, B (n 32)) were used. Half of the ewes were trickle infected with 30,000 larvae of the abomasal parasite Teladorsagia circumcincta per week and the other half were not. During the experiment, all ewes had ad libitum access to a low-protein diet that provided less protein than the recommended allowance. In addition, half of the ewes received a protein supplement that resulted in protein intakes that exceeded recommendations. Nematode infection resulted in a breakdown of immunity to parasites and a reduction in food intake in both breeds. The breeds differed in the extent of PPRI (G ewes having higher faecal egg counts than B ewes), but not in the magnitude of anorexia. Protein supplementation resulted in a reduction in faecal egg counts, but had no effect on the magnitude of anorexia. Plasma leptin concentrations changed significantly over time, but were not affected by protein supplementation or infection. It is concluded that infection with T. circumcincta in periparturient ewes results in anorexia that is not alleviated by protein supplementation and seems unrelated to plasma leptin concentrations.

The influence of protein supplementation on the immune response to Haemonchus contortus.

A major protective mechanism in lambs against the abomasal parasite Ostertagia (Teladorsagia) circumcincta appears to be the immunoglubulin (Ig)A-mediated suppression of worm growth and fecundity. The present study indicates that IgA may play a similar role in the control of another abomasal parasite Haemonchus contortus. Hampshire Down lambs were offered one of two diets: (i) a basal diet and (ii) a diet supplemented with additional protein. Lambs were then 'trickle' infected with H. contortus and killed 10 weeks after the start of infection. Those lambs on the supplemented diet had shorter adult worms and produced significantly more antiparasite IgA. There was a significant association between reduced female adult worm length and increased IgA against third-stage larvae. Most of the difference between the two groups in worm length could be accounted for by differences in IgA responses. Therefore, IgA may be the major mechanism controlling fecundity of H. contortus and the magnitude of the IgA response is influenced by the quality of the diet.

Anaemia in housed lambs: effects of oral iron on clinical pathology and performance.

An experiment including 39 pairs of housed twin lambs was performed to evaluate the effect of an oral iron supplement (Fe-MAX Starter) on clinical pathology, growth rates and disease occurrence. Significant differences between the iron supplemented group (Fe-group) and the controls were seen, for varying periods of time, for all red blood cell and iron parameters examined. In spite of this, 25% of the iron supplemented lambs had haemoglobin values below 80 g/L 4 weeks after treatment, whereas 33% of the controls had corresponding values 3 weeks after treatment, indicating that one single iron dose was insufficient to prevent iron deficiency anaemia. No significant positive effect on live weights was seen. However, the Fe-group had a poorer daily weight gain during the first week after dosing (p < 0.01), but a better daily gain during the second (p < 0.01) and third weeks. No effects were seen on disease occurrence. An additional trial with iron dextran injections to 5 untreated 21 days old lambs with varying haemoglobin values, revealed a rapid increase in the red cell distribution in anaemic lambs, with production of macrocytic, mainly normochromic erythrocytes. The new erythrocyte population was visible on the cytogram after 2 to 3 days and on the histogram after 5 days.

Establishment and fecundity of Ostertagia circumcincta and Trichostrongylus colubriformis in lambs fed lotus (Lotus pedunculatus) or perennial ryegrass.

Forty four 12-14 week old Polled Dorset ram lambs, raised helminth free from birth, were used to investigate the effects of condensed tannins (CT) in lotus (Lotus pedunculatus) on lamb growth and gastrointestinal nematode establishment and fecundity. Condensed tannins bind to proteins in the rumen and increase the flow of protein to the intestines. Lambs were allocated to either a ryegrass (Lolium perenne) or lotus diet fed ad libitum, with or without twice daily drenching of polyethylene glycol (PEG) which binds with and deactivates the CT. One week after allocation to the diets, each lamb was infected per os with 10,000 Ostertagia circumcincta and 10,000 Trichostrongylus colubriformis larvae and slaughtered 28 or 29 days later. Lambs fed lotus had lower faecal egg counts (P < 0.0001) and lower O. circumcincta burdens (P < 0.001), fewer female O. circumcincta (P < 0.0001) and higher faecal dry matter (P < 0.001) than lambs fed ryegrass, but numbers of T. colubriformis nematodes were not affected. This trial did not ascribe beneficial effects of L. pedunculatus to CT per se and the use of PEG does not seem appropriate to studies of parasitology.

Effect of aflatoxin in growing lambs fed ruminally degradable or escape protein sources.

Thirty-two crossbred (Suffolk x Rambouillet) wether lambs were used to examine the effectiveness of protein source (soybean meal [SBM] or fish meal [FM]) in alleviating decreased performance associated with dietary aflatoxin (AF) in growing lambs. After a 21-d adaptation period to concentrate diets, lambs were assigned to the following dietary treatments: 1) SBM, 0 mg of AF; 2) FM, 0 mg of AF; 3) SBM + 2.5 mg of AF/kg diet; or 4) FM+2.5 mg of AF/kg diet (two lambs/pen; four pens/treatment). Diets were fed 35 d, at which time AF was removed from the diet (except one pen/protein source) and lambs continued on study for an additional 32 d. On d 67, all lambs were killed and necropsied. Average daily gain, feed intake, and gain/feed were similar (P > .10) among lambs fed SBM or FM; however, lambs fed AF had lower (P < .01) feed intakes, daily gain, and gain/feed. Feed intake remained lower (P < .01) after AF was removed from the diet. Aflatoxin elevated (P < .01) aspartate amino transferase and gamma-glutamyl transferase activities and total protein and cholesterol concentrations while decreasing (P < .05) alkaline phosphatase, glucose, cholinesterase, albumin, inorganic phosphorus, iron, and total-iron-binding capacity. Hematocrit, white blood cell count, and prothrombin time increased (P < .01) in lambs fed AF. No AF or protein effects were seen on ruminal VFA, pH, or lymphocyte blastogenesis (P > .10).(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of protein intake on per os zinc deficiency treatment in sheep.

Two experiments were conducted on 20 male 3.5 month-old Limousin X Romanoff lambs, weighing between 30 and 35 kg. They received a zinc deficient diet based on 50% late harvested hay and 50% barley straw containing from 8 mg Zn/kg dry matter to 11.7 mg Zn/kg dry matter and sprayed with caramel. Sheep were hypozincaemic from the 14th or 21st day. In the first experiment, the zinc level of the diet (94 g crude protein/kg DM from urea) was increased to 50 mg Zn/kg dry matter on the 35th day. At the same time, half the animals received egg albumin instead of urea; both diets were isoproteic. No change in zincaemia was observed in either of the two groups: it remained low. On day 51, the albumin group received an increase in dietary protein by the addition of more egg albumin, so that the diet contained up to 148 g crude protein/kg dry matter, the usual requirements of growing lambs. The zincaemia of these sheep started to increase and was restored to normal with a diet that contained 150 mg Zn/kg dry matter. The zincaemia of the low protein group remained unchanged whatever the zinc level. In the second experiment, increasing the zinc level with the diet (70 g crude protein from egg albumin) from 11.6 to 300 mg/kg dry matter restored the zincaemia either in the high protein group (140 g crude protein/kg dry matter) or in the low protein group (70 g crude protein/kg dry matter).(ABSTRACT TRUNCATED AT 250 WORDS)

Bent-limb syndrome in lambs raised in total confinement.

A bent-limb syndrome in lambs raised in total confinement was characterized by curvature of the forelimbs. Radiographic findings included flaring of the affected long bone and thinning of the growth plate. The main histologic change was endochondral dysplasia of the long bone. In feed samples, all trace minerals analyzed were within recommended concentrations except iron, which was much higher (400 ppm dry matter) than the normal requirement of lambs (70 ppm). All mineral concentrations in serum were normal except those of inorganic phosphorus and iron, which were higher. Results of soft tissue and bone mineral analyses were normal. Altering the ratio of calcium and phosphorus did not affect the incidence of disease, but intramuscular administration of massive doses of vitamin D3 and reducing the amount of dietary iron had a prophylactic effect. The increase in serum phosphorus was probably related to the dietary excess of iron, which probably decreased vitamin D metabolite formation in the kidney, which in turn could be prevented by massive doses of vitamin D3.

Deaths from copper toxicity of sheep at pasture and the use of fresh seaweed.

A number of sheep of the Orkney breed died of suspected copper poisoning while at pasture under circumstances which left sheep of other breeds apparently unaffected. Fresh seaweed offered to sheep with symptoms of copper toxicity appeared to be therapeutic and to lead to a reduction in plasma Cu level.