Biological Control of Sheep Parasites using Duddingtonia flagrans: Trials on Commercial Farms in Sweden

   

Trials were conducted on 3 commercial sheep farms in Sweden to assess the effect of administering spores of the nematode trapping fungus, Duddingtonia flagrans, together with supplementary feed to lactating ewes for the first 6 weeks from turn-out on pastures in spring. Also control groups of ewes, receiving only feed supplement, were established on all 3 farms. Groups were monitored by intensive parasitological investigation. The ewes and their lambs were moved in late June to saved pastures for summer grazing, the lambs receiving an anthelmintic treatment at this time. After approximately 6 weeks on summer pasture the lambs were weaned, treated a second time with anthelmintic, and returned to their original lambing pastures for finishing. Decisions as to when lambs were to be marketed were entirely at the discretion of the farmer co-operators. No difference in lamb performance was found between the two treatments on all three farms. This was attributed to the high levels of nutrition initially of the ewes limiting their post-partum rise in nematode faecal egg counts in spring, which in turn resulted in low levels of nematode infection on pastures throughout the autumn period. Additionally, pastures were of good quality for the lambs during the finishing period, so they grew at optimal rates as far as the farmers were concerned.     

Merino ewes bred for parasite resistance reduce larval contamination onto pasture during the peri-parturient period

The peri-parturient period is crucial for controlling worms as the acquired immunity of ewes is disrupted, resulting in an increase in faecal worm egg counts. Two hypotheses were tested in this experiment - that ewes bred for worm resistance would have lower faecal worm egg counts than unselected control ewes, during late pregnancy and lactation, under similar but separate grazing areas; and also that numbers of infective nematode larvae would be lower on pastures grazed by resistant ewes than pastures grazed by unselected control ewes. Faecal samples were collected from resistant and unselected ewes in late pregnancy and early lactation, during the winter rainfall season, and analysed for numbers of Trichostrongylus colubriformis and Teladorsagia circumcincta. Pasture samples were taken 1 week before and 7 weeks after lambing started and analysed for infective larvae. In all sheep, worm egg counts rose 2 weeks prior to lambing and continued into lactation. Worm egg counts were significantly lower in the resistant ewes from 1 week before lambing to 2 weeks after lambing. There were no differences in egg counts between single- and twin-bearing ewes in the resistant line. However, twin-bearing control ewes had significantly higher egg counts than single-bearing control ewes. Following lactation, plots grazed by resistant ewes had substantially less contamination with T. colubriformis larvae, but there were no differences in numbers of T. circumcincta larvae. Our results demonstrate that sheep bred for worm resistance has lower worm burdens during the peri-parturient phase and that lambs born to resistant ewes face a lower larval challenge during their introduction to grazing. In our environment, selection for low worm egg counts has produced sheep highly resistant to T. colubriformis, but has had less impact on resistance towards T. circumcincta.     

Toxoplasmosis in Sheep

The epidemiology of toxoplasmosis in sheep was studied during a period of 31/2 to 6 years in 4 flocks in which abortions from the infection previously had occurred. The epidemiological pattern indicated that a heavy contamination of the environment may persist for about 2 years. Even in flocks with an apparently normal reproductive performance, toxoplasmosis may cause barrenness, abortion or delivery of dead lambs in 1–2 % of the breeding ewes. The prevalence of infected sheep increased with the age. The incidence of infection was significantly lower in 6–12 months old lambs than in mature ewes. The incidence of infection was higher on lowland pastures than on mountain pastures in not populated areas. On lowland pastures the incidence of infection was lower during the summer than during the winter. kw|Keywords|k]toxoplasma infection; k]epidemiology; k]sheep {fn1|This work was supported by grants from the Norwegian Research Council for Science and for the Humanities.}     

Control of nematode parasites by grazing management—II. Decontamination of sheep and cattle pastures by varying periods of grazing with the alternate host

Commencing in December 1970, paddocks of a uniform series of sheep pastures were grazed for 6, 12 or 24 weeks by either yearling steers is or yearling ewes. Cattle pastures were treated similarly. All ewes and steers were pre-dosed with anthelmintic.At the conclusion of alternate grazing the effectiveness of the grazing treatments was evaluated by grazing each paddock for 1 month with either ten worm-free lambs (sheep pastures) or three wormfree calves (cattle pastures). The test animals were then slaughtered for total worm counts. The grazing of sheep pastures with cattle for 6, 12 or 24 weeks from December onwards resulted in reductions in numbers of Haemonchus contortus and Trichostrongylus colubriformis in test lambs. In comparison with continuous grazing by sheep, Nematodirus spp was only reduced after 24 weeks grazing by cattle. Cattle pastures grazed by sheep for 6 weeks showed no reduction in numbers of Ostertagia ostertagi or Cooperia oncophora in test calves. However after 12 weeks with sheep, numbers of O. ostertagi though not C. oncophora were reduced and after 24 weeks of alternate grazing both these species were reduced.Calves following the 6 week sheep treatments acquired both Haemonchus contortus and Trichostrongylus colubriformis and the calves from the 12 week sheep treatment paddock also carried H. contortus. For sheep the only evidence of cross-transmission was the occurrence of small numbers of Cooperia oncophora in test lambs from the 24 week cattle grazing treatment.The results provide evidence that sequential stocking with cattle and sheep in conjunction with anthelmintic treatment is an effective management strategy for preparing parasitologically safer pastures, but further information is required to determine the optimum timing of sequential stocking in farming situations.     

Winter Resistant Oocysts in the Pasture as a Source of Coccidial Infection in Lambs

Lambs born in pens with slatted floor were brought out at 2–5 weeks of age on pastures heavily grazed by sheep the previous years. About 16 days later the oocyst output of the lambs rapidly increased to high levels. Lambs on pastures which never had been grazed by sheep earlier, had moderate oocyst counts. Between 11 and 25 days after the beginning of grazing there were significantly more lambs with diarrhoea on permanent pastures compared with pastures never grazed by sheep earlier. It was found that lambs were heavily infected during the first 2 days on permanent pastures. Thirteen housed lambs were given 10–50 g of soil from a permanent pasture as a water suspension by a stomach tube. Fifteen days later there was a steep rise in the oocyst output in most of them, and 11 of the 13 lambs developed diarrhoea and 2 died. None of 10 lambs given uninfected soil and none of 12 untreated controls showed diarrhoea and the oocyst output remained on a moderate level. It is concluded that oocysts which have survived the winter in the pasture are the main source of infection with Eimeria spp. in lambs with this kind of management. Soil-eating is the most likely source of infection during the first days on pasture.     

A model for nematodiasis in New Zealand lambs: The effect of drenching regime and grazing management on the development of anthelmintic resistance

A model for nematodiasis in lambs was expanded to incorporate both the contribution of ewes to nematode epidemiology and the genetic parameters required to simulate the development of anthelmintic resistance in the nematode population. The expanded model was used to assess the impact of various drench and grazing management strategies for ewes and lambs on the rate of development of anthelmintic resistance. Three grazing management options, under a range of drenching schedules, were compared: one in which lambs and ewes were rotationally grazed as separate flocks over the same area after weaning (common grazing); a second in which lambs were grazed, after weaning, on areas from which ewes were excluded (separate grazing); and a third in which lambs were moved to “safe” pasture at weaning and again in early autumn (integrated control). Drenching strategies examined under the first 2 grazing options included a 5 lamb-drench “preventive” programme with 0, 1, 2, 3 or 4 additional lamb drenches, and 0 or 1 ewe drench treatment at either tail-docking or mating. Under the third grazing option, lambs were given either 1 or 2 drench treatments at or following each move to safe pasture and ewes 0 or 1 drench treatment at either tail-docking (i.e., 3–4 weeks after lambing) or mating. Model output suggests that drenching ewes prior to any lamb drenching programme is likely to significantly increase selection for drench resistance by pre-selecting the larval challenge to the lambs and, under some grazing systems, by reducing the diluting effect of eggs of susceptible genotypes passed by undrenched ewes. The results highlight the potential importance of undrenched ewes as a refuge for susceptible worm genotypes and indicate that on its own, drenching frequency is likely to be a poor indicator of selection pressure for resistance and thus of limited value in selecting strategies for the management of anthelmintic resistance.     

Serological Investigation of Granulocytic Ehrlichia Infection in Sheep in Norway

Serum samples of 749 sheep from 75 sheep flocks in Norway, i.e. 361 lambs (6 to 7 months old) and 388 adults (>1.5 year), were analysed for antibodies to Ehrlichia equi. Ten animals from each flock were examined. Seropositive animals were found along the coast of southern Norway from Vestfold to S?r-Tr?ndelag (as far north as 63°38'N). Seropositive sheep were not found in southeast, east or northern Norway. Thirty-two flocks were seropositive, although tick-borne fever had only been diagnosed earlier in half of these. In 78% of the seropositive flocks, more than 80% of the sheep were seropositive. A total of 35.7 % and 36.3 % of lambs and adults were found seropositive, respectively. However, the overall seroprevalence among animals that had been grazing on Ixodes pastures were 0.80 for the lambs and 0.84 for the adults. Mean antibody titres (± SD) (log₁₀) in seropositive lambs and adults were 2.59 (± 0.449) and 2.70 (± 0.481), respectively. No significant differences in either seroprevalence or mean antibody titre between sheep of different ages were obtained in this study. Based on antibodies 94% of sheep flocks on Ixodes pastures were infected with a granulocytic Ehrlichia infection. The association between seropositive flocks and Ixodes infested pasture shows a very high degree of agreement (p < 0.00001). The present study indicates that granulocytic Ehrlichia infection in sheep is underdiagnosed in Norway.     

Effect of genetic type, lactation and management on helminth infection of ewes in an intensive grazing system on irrigated pasture.

A survey of helminth infection was conducted in a flock of 290 ewes distributed into Romanov (R), Merinos d'Arles (M) and Romanov x Merinos (R x M) genetic types, grazing irrigated pasture in the south of France. Faecal egg and larval counts were done seven times per year from 1981 to 1984 on homogeneous groups of ewes and then individually once to four times every autumn from 1985 to 1988. Helminth fauna was diverse and more abundant during autumn. High levels of strongyle infection occurred in the ewes that remained on the same irrigated pastures during summer. Moving to Alpian pastures during the summer lowered autumnal infection. Significant differences between genotypes in intensity of infection were observed in the order R > R x M > M for strongyles (Teladorsagia circumcincta and/or Trichostrongylus vitrinus, Chabertia ovina and/or Oesophagostomum venulosum, Nematodirus spp.), Moniezia spp. and Dictyocaulus filaria. The hierarchy was reversed for Fasciola hepatica infection and not consistent from one year to another for protostrongylid infections. The effect of lactation intensity on the postparturient rise was studied by equilibrating number of ewes according to reproductive status (zero, one or two lambs in lactation). Merino ewes with two lambs in lactation, as well as primiparous Romanov ewes, had significantly higher strongyle infections than the others. The repeatabilities of the larval and egg counts between the four trial years were 0.24, 0.23 and 0.16, respectively, for protostrongyles, Nematodirus and strongyles, with higher intra-annual values for protostrongyles and inconsistently significant results for strongyles due to the presence of several species.     

Evaluation of Copper Supplementation to Control <Emphasis Type="Italic">Haemonchus contortus</Emphasis>Infections of Sheep in Sweden

A pen study was conducted to assess the effect of providing daily copper mineral supplement, or copper wire particle (COWP) capsules, on established or incoming mixed nematode infections in young sheep. For lambs with established (6 week old) infections, COWP resulted in 97% and 56% reduction of the adult and early L4 stages of H. contortus, respectively, compared with controls (p < 0.001). Additionally there was a 74% reduction in Teladorsagia circumcincta infections in the COWP lambs compared with controls (p < 0.01). However, no effect was observed when COWP were given at the commencement of a larval dosing period of 6 weeks. There was no significant effect of copper mineral supplement (given at the recommended rate to prevent Cu deficiency) on either established, or developing parasite infections. In addition, a field trial was conducted on a commercial farm to assess the effects of COWP in the management of recurrent H. contortus infections, but lack of parasites during the grazing season prevented an adequate assessment from being made. These results indicate that there is little, if any, benefit from a parasite control standpoint in recommending copper therapy, specifically to control parasites in Swedish sheep flocks.     

Normal color variations of the canine ocular fundus,a retrospective study in Swedish dogs

Background

Anthelmintic treatment is the most common way of controlling nematode infections in ruminants. However, several countries have reported anthelmintic resistance (AR), representing a limitation for sustainable small ruminant production. The knowledge regarding worm control management represents a baseline to develop a guideline for preventing AR. The aim of the present study was therefore to improve our knowledge about the worm control practices in small ruminant flocks in Norway.

Methods

A questionnaire survey regarding worm control practices was performed in small ruminant flocks in Norway. Flocks were selected from the three main areas of small ruminant farming, i.e. the coastal, inland and northern areas. A total of 825 questionnaires, comprising 587 sheep flocks (return rate of 51.3%) and 238 goat flocks (52.6%) were included.

Results

The results indicated that visual appraisal of individual weight was the most common means of estimating the anthelmintic dose used in sheep (78.6%) and goat (85.1%) flocks. The mean yearly drenching rate in lambs and ewes were 2.5 ± 1.7 and 1.9 ± 1.1, respectively, whereas it was 1.0 (once a year) in goats. However, these figures were higher in sheep in the coastal area with a rate of 3.4 and 2.2 in lambs and ewes, respectively. Benzimidazoles were the predominant anthelmintic class used in sheep flocks (64.9% in 2007), whereas benzimidazoles and macrocyclic lactones were both equally used in dairy goat flocks. In the period of 2005-2007, 46.3% of the sheep flocks never changed the anthelmintic class. The dose and move strategy was practiced in 33.2% of the sheep flocks.

Conclusions

The present study showed that inaccurate weight calculation gives a risk of under-dosing in over 90% of the sheep and goat flocks in Norway. Taken together with a high treatment frequency in lambs, a lack of anthelmintic class rotation and the common use of a dose-and-move strategy, a real danger for development of anthelmintic resistance (AR) seems to exist in Norwegian sheep and goat flocks. This risk seems particularly high in coastal areas where high treatment frequencies in lambs were recorded.     

Using lamb sales data to investigate associations between implementation of disease preventive practices and sheep flock performance

Although the UK is the largest lamb meat producer in Europe, there are limited data available on sheep flock performance and on how sheep farmers manage their flocks. The aims of this study were to gather evidence on the types of disease control practices implemented in sheep flocks, and to explore husbandry factors associated with flock productivity. A questionnaire focusing on farm characteristics, general husbandry and flock health management was carried out in 648 farms located in the UK over summer 2016. Abattoir sales data (lamb sales over 12 months) was compared with the number of breeding ewes on farm to estimate flock productivity (number of lambs sold for meat per 100 ewes per farm per year). Results of a multivariable linear regression model, conducted on 615 farms with complete data, indicated that farms vaccinating ewes against abortion and clostridial agents and administering a group 4/5 anthelmintic to ewes (as recommended by the Sustainable Control of Parasites in Sheep Initiative) during quarantining had a greater flock productivity than farms not implementing these actions (P<0.01 and 0.02, respectively). Flocks with maternal breed types had higher productivity indexes compared with flocks with either pure hill or terminal breeds (P<0.01). Farms weighing lambs during lactation had greater productivity than those not weighing (P<0.01). Importantly, these actions were associated with other disease control practices, for example, treating individual lame ewes with an antibiotic injection, weaning lambs between 13 and 15 weeks of age and carrying out faecal egg counts, suggesting that an increase in productivity may be associated with the combined effect of these factors. This study provides new evidence on the positive relationship between sheep flock performance and disease control measures and demonstrates that lamb sales data can be used as a baseline source of information on flock performance and for farm benchmarking. Further research is needed to explore additional drivers of flock performance.     

Reduced Weight Gain Due to Subclinical Anaplasma phagocytophilum (Formerly Ehrlichia phagocytophila) Infection

Tick-borne fever (TBF) is caused by the rickettsia Anaplasma phagocytophilum (formerly Ehrlichia phagocytophila) and is a common disease in sheep in areas of Norway infested by Ixodes ricinus ticks. TBF can cause both direct and indirect losses to sheep kept on tick-infested pastures. In the present work we studied a sheep flock of 26 ewes and 50 lambs on pasture from May until September. No cases of TBF had earlier been observed on this pasture. Blood samples from lambs with a reduced weekly weight gain were collected and analysed for A. phagocytophilum infection by blood smear examination. In addition, at the end of the study, sera from all lambs were analysed by an indirect fluorescent antibody assay (IFA) to determine the antibody titre to E. equi. No clinical signs of tick-borne infections were observed, except in one lamb. However, 30 (60%) of the lambs grazing on this pasture became infected with A. phagocytophilum, and the infected lambs had a reduced weight gain (mean) of 3.8 kg compared with the uninfected lambs. The present study indicates that A. phagocytophilum infection may be widespread and contribute to considerable productivity losses even on pastures with no apparent tick infestation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Comparison of Worm Control Strategies in Grazing Sheep in Denmark

Control of nematode parasites with reduced reliance on the use of anthelmintics was studied in 16 ewes with suckling twin lambs on contaminated pasture in Denmark. Ewes and lambs were treated with albendazole at turn-out 3 May. Ewes were removed from the groups on 26 July, and lambs were slaughtered on 11 October. The animals were allocated to 4 groups of 8 lambs and their 4 ewes. Group TS was treated with albendazole at weeks 3, 6 and 8 after turnout and set-stocked; group TM was similarly treated but moved to clean pasture in conjunction with the last drenching; group US was untreated and set-stocked, and group UM was left untreated but moved to clean pasture week 8 after turn-out. Supplementary feed was offered in June and August due to scarcity of pasture. Strategic treatments of ewes and lambs weeks 3, 6 and 8 after turn-out, with or without a move to clean pasture, were highly effective in controlling nematode infections for most of the season. This was reflected in better weight gains and carcass characteristics in the treated compared to untreated lambs, resulting in an average increase in the value of the product by 36%. The effect of moving without treatment (UM) on faecal egg counts was limited but peak pasture infectivity was reduced to less than 10% compared to the set-stocked group and weight gains of lambs were significantly better despite poor feed availability in late season. The study showed that under set-stocked conditions repeated anthelmintic treatments of both ewes and lambs in early season may ensure sufficient nematode control whereas moving animals to clean pasture without dosing was less efficient. The latter may, however, still be a viable option in organic and other production systems where routine use of anthelmintics is banned, particularly if weaning and moving are combined or a second move is performed.     

Grazing behaviour and performance of lactating suckler cows, ewes and goats on partially improved heathlands

The foraging behaviour (grazing time and diet composition), live-weight (LW) changes and parasitic infection (faecal egg counts of gastrointestinal nematodes) of 12 beef cows, 84 ewes and 84 goats suckling their offspring, managed in mixed grazing on heathlands with 24% of improved pasture of perennial ryegrass-white clover, were studied during the years 2003 and 2006. The results showed that goats tended to graze for a longer time, and utilised significantly more heathland vegetation than cattle and sheep, including in their diet in an average of 0.39 herbaceous plants, 0.11 gorse and 0.51 heather over the grazing season, comparing with respective mean values of 0.85, 0.02 and 0.13 in cattle and sheep. Dietary overlap was higher between cattle and sheep (0.76) than between sheep and goats (0.53) or between cattle and goats (0.47). Despite the high performance of autumn-calving cows in spring, sheep had the best LW changes per livestock unit (LU) during the whole grazing season. Goats' performance per LU was lower than in sheep but higher than in spring-calving cows. Regarding offspring production, lambs had higher LW gains per LU than calves and kids. Mean nematode eggs/g fresh faeces (epg) during the grazing season were higher in goats (91 epg) compared with sheep (34 epg) and cattle (14 epg), particularly from September to December. In conclusion, sheep performed best on these heathlands with improved pasture areas if the entire grazing season was considered, despite the good level of production in spring from autumn-calving cows. The results suggested the complementary use of goats in order to increase the effective utilisation of the available vegetation, achieving production levels similar to those from spring-calving cows. Therefore, mixed flocks of sheep and goats would be the most appropriate sustainable systems from the animal production and vegetation use points of view.     

Identification of quantitative trait loci affecting resistance to gastrointestinal parasites in a double backcross population of Red Maasai and Dorper sheep

A genome‐wide scan for quantitative trait loci (QTL) affecting gastrointestinal nematode resistance in sheep was completed using a double backcross population derived from Red Maasai and Dorper ewes bred to F₁ rams. This design provided an opportunity to map potentially unique genetic variation associated with a parasite‐tolerant breed like Red Maasai, a breed developed to survive East African grazing conditions. Parasite indicator phenotypes (blood packed cell volume – PCV and faecal egg count – FEC) were collected on a weekly basis from 1064 lambs during a single 3‐month post‐weaning grazing challenge on infected pastures. The averages of last measurements for FEC (AVFEC) and PCV (AVPCV), along with decline in PCV from challenge start to end (PCVD), were used to select lambs (N = 371) for genotyping that represented the tails (10% threshold) of the phenotypic distributions. Marker genotypes for 172 microsatellite loci covering 25 of 26 autosomes (1560.7 cm ) were scored and corrected by Genoprob prior to qxpak analysis that included Box–Cox transformed AVFEC and arcsine transformed PCV statistics. Significant QTL for AVFEC and AVPCV were detected on four chromosomes, and this included a novel AVFEC QTL on chromosome 6 that would have remained undetected without Box–Cox transformation methods. The most significant P‐values for AVFEC, AVPCV and PCVD overlapped the same marker interval on chromosome 22, suggesting the potential for a single causative mutation, which remains unknown. In all cases, the favourable QTL allele was always contributed from Red Maasai, providing support for the idea that future marker‐assisted selection for genetic improvement of production in East Africa will rely on markers in linkage disequilibrium with these QTL.     

Sheep blowfly strike risk and management in Great Britain: a survey of current practice

Abstract.  The methods used for the control of sheep blowfly strike (ovine cutaneous myiasis) and the farm management factors associated with strike prevalence were examined using data from questionnaire survey returns provided by 966 sheep farmers in Great Britain, based on the period between March 2003 and February 2004. Overall, 91% of participants treated prophylactically with insecticides against blowfly strike; 39% treated twice and 11% treated more than three times in the year. Insect growth regulators (IGRs) were the most commonly chosen product (40%), especially the IGR cyromazine. Only 12% of farmers opted to dip their sheep in organophosphate insecticide against fly strike and 2% of farmers reported applying inappropriate products against strike to their sheep, such as ivermectin or 'drenches'. Farmers worming their ewes more often were 0.8 times less likely to report blowfly strike, but those who wormed their lambs more often were 1.2 times more likely to report strike. Pure-breed flocks were 0.7 times less likely to record an outbreak of blowfly strike than cross-breed flocks. Strike was less likely in ewe flocks grazed at higher altitude; however, this relationship with altitude was not seen in lambs. The results show that insecticides remain the primary tool used by almost all farmers to prevent strike and that the type of insecticides used and means of application have altered dramatically over the past 15 years. However, the prevalence of strike has remained almost unchanged over this period. Clearly careful attention to the type and timing of insecticide application, in association with a detailed understanding of the husbandry factors that predispose sheep to higher strike risk, is essential to allow the optimal management of strike problems.     

Persistence of Granulocytic Ehrlichia Infection During Wintertime in Two Sheep Flocks in Norway

Granulocytic Ehrlichia infection in sheep is common in Norway in areas with Ixodes ricinus. In this study, 2 sheep flocks that had been grazing on I. ricinus infested pastures the previous season, were blood sampled after being housed indoors for nearly 6 months during wintertime. Thirty animals from each flock were examined for granulocytic Ehrlichia infection in the peripheral blood by blood inoculation studies, stained blood smear evaluation, polymerase chain reaction (PCR) analysis and serology (IFAantibodies). The animals were sampled twice within a three-week period, the first time before and the second time after lambing. Two sheep in one flock were found Ehrlichia positive by both blood smear evaluation and PCR before lambing, and 3 sheep were found positive after lambing; 2 by blood smear examination and 3 by PCR. In the other flock, no sheep was found infected before lambing, but 2 ewes were found positive after lambing by both blood smear evaluation and PCR. In the first flock, 87% of the animals were found seropositive before lambing, and the mean antibody titre (log 10 ± SD) to E. equi was 2.45 ± 0.401. In the second flock, 40% were found seropositive before lambing, and the mean antibody titre was 1.93 ± 0.260. Seroprevalence and mean antibody titre in these 2 flocks were significantly different (p < 0.001). The present study indicates that sheep may be a reservoir host for granulocytic Ehrlichia infection from one grazing season to the next under natural conditions in Norway.     

Nematode parasitism in sheep in North-East England: The epidemiology of Ostertagia species

This investigation was undertaken to determine the epidemiology of a single parasite genus, Ostertagia, in natural parasite populations in sheep raised under intensive conditions in North-East England.Over the 2 years of study, striking differences were found in the overall level of parasitism which were related to different climatic conditions, specifically rainfall. Despite the low source of infection derived from the ewes grazing on clean pasture in 1973 the overall level of parasitism in the lamb crop was high, this was attributed to the ideal climatic conditions for parasite translation during Spring and Summer. Ostertagia spp. was found to survive well over Winter and to initiate early infections in the young lambs in the following year. Despite the two sources of egg contamination, from the ewes and lambs, unusually dry conditions were experienced from March to June which resulted in much lower levels of infection in the second year of investigation.Regulation of the parasite population within the lambs was clearly demonstrated. Inhibition of Ostertagia was recorded somewhat earlier in the season than had been hitherto reported and was considered to be induced by a multiplicity of factors.     

Maternal grazing on stubble and Mediterranean shrubland improves meat lipid profile in light lambs fed on concentrates

Concentrates-fed lamb meat is often associated with an unfavourable lipid profile (high levels of saturated and/or n-6 polyunsaturated fatty acids; SFA and PUFA). For this reason, Spanish sheep producers from Mediterranean areas are turning to traditional grazing by ewes to obtain healthier lamb meat. The objective of this research was to determine the effects of maternal grazing on the fatty acid (FA) composition of weaned lamb meat. The ewes (Segureña breed) were allocated to two different rearing systems during pregnancy (5 months) and lactation (45 days): (i) feeding indoors on barley grain and lucerne pellets; (ii) grazing on cereal stubble, fallow land and seasonal pastures consisting of Mediterranean shrubs, herbs and trees. Two groups of 20 autumn and spring lambs were sampled. The lambs were weaned at 13.1±0.9 kg and 45.0±4.1 days age and fed on grain-based concentrates until they reached 24.8±2.1 kg live weight (light lambs slaughtered at 98.3±3.6 days of age). The FA content was determined in the intramuscular loin fat by gas chromatography using a flame ionization detector. The ewe diet did not affect the levels of the main lamb FAs (C18:1c+t, C16:0 and C18:2c), and so did not provide any additional reduction in fat saturation. Saturated fatty acids represented around 40% of total FAs determined in the meat. Ewe grazing acted as an n-3 PUFA-promoting diet, providing a lamb meat with a lower n-6/n-3 ratio. Spring lamb meat had higher proportions of n-3 PUFA (C18:3n-3, C20:5, C22:5 and C22:6) and conjugated linoleic acid (C18:2c9t11+c11t9) to the detriment of the n-6 PUFAs (C20:4, C20:2 and C22:4), while autumn lamb meat also had higher levels of C18:3n-3 and C18:3n-6, and lower level of C20:4, which points to little seasonal differences. The n-6/n-3 ratio achieved by ewe grazing fell from 8.2 to 4.1 (Spring) and from 7.6 to 5.5 (Autumn), values which are close to those recommended in human diet for good cardiovascular health. These n-6/n-3 reductions were associated with lower levels of total PUFA and C20:4n-6. Our research concluded that grazing on stubble and Mediterranean shrubland by ewes, a sustainable rearing practice involving local agro resources, contributed to obtaining weaned lamb meat with a more favourable lipid profile and so can be recommended to sheep farmers.     

Dynamics of infestation of tracers lambs by gastrointestinal helminths under a traditional management system in the North of Tunisia

The authors present a survey of gastrointestinal helminths of sheep on permanent pastures in the extreme north region of Tunisia (Mediterranean climate). Dynamic infestation of animals has been monitored by using batches of three tracer lambs introduced each two months during 2004 and 2005. These lambs were kept in the pens of veterinary school of Sidi Thabet (Tunisia) during three months and then necropsied. Faecal and blood samples were took from tracer lambs each two months during the whole period, and from animal flock only during 2004. The main helminth genera encountered were Trichostrongylus spp., Teladorsagia spp., Strongyloides papillosus and Anoplocephalidea; occasionaly were found Nematodirus, Oesophagostomum, Chabertia, Cooperia, Trichuris and Paramphistomum. The egg count of the ewes and lambs in the flock showed two peaks. For both ewes and lambs there is a gradual increase from January with a peak in May-June. This first peak is considered to be due to acquisition of infective larvae during the rainy and cold season, as evident from the worm burdens of tracer lambs. The second peak was exclusively observed in ewes during late autumn-early winter (November-December); it has two origins: infestation by third larvae stage and the periparturient rise. The worm burdens of tracer lambs showed that there was a gradual accumulation of nematodes from September- October, reaching a peak in March-April; a very low or naught infection is reported during the dry period (July-August). Infection by Anoplocephalidea was higher during the dry season. This study is primordial for a comprehensive control programme implementation against gastrointestinal helminths.