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1.
SUMMARY While the radical Mules operation reduced the incidence of breech strike from 59% to 13% in scouring sheep, the problem was further alleviated by docking lambs' tails at the correct (medium) length. Docking lambs' tails very short strongly predisposed radically mulesed ewes and wethers to faecal soiling and breech strike (20% struck). Radically mulesed sheep with tails docked midway down the vulval orifice in ewes, and the corresponding length in wethers, were rarely struck (3%) and did not appear to require crutching to prevent breech strike associated with scouring or urine staining.  相似文献   

2.
A field survey was undertaken between 1972-76 to reappraise the nature of the blowfly problem in New South Wales. For 2 years, 1972-1974, some 80,000 sheep were kept under observation and 12,481 strikes were reported, most due to Lucilia cuprina. Breech strike was still the basic problem but tail strike associated with scouring had become an important component where pastures have been improved. Breech strike was controlled at minimal cost by managerial practices such as docking tails the correct length--second joint-space palpable ventrally (midway down the vulval orifice in ewes) for radically mulesed lambs and the third joint-space (tip of vulva in ewes) for all other lambs-mulesing at lamb marking, mid-season crutching, determining the cause of scouring and applying the appropriate preventative or remedial measures. Thus the use of insecticides could be reserved for the control of body strike in young sheep in the odd wet years and poll strike in horned rams. Major outbreaks of body strike occurred in 1973/74. Body strike worried graziers most because of its unpredictability, sudden onset and scale. and only failing insecticides were available for control.  相似文献   

3.
Comparison was made of the performances of cross-bred ewes and their lambs on pastures of low helminth infectivity ("safe" pastures) or contaminated pastures and at high or low stocking rates. Ewes grazing the safe, but not the contaminated, pastures were given a single pre-lambing drench. The largest difference in parasite infection between treatments was the level of exposure of sheep to Trichostrongylus spp, which was negligible on the safe pastures. The effects of parasite control on lamb growth were significant only in twins during the last 2 months before weaning. However, 22% of lambs on contaminated plots became soiled in the breech area and 38% were flystruck, compared with 8% and 10% respectively for lambs on the safe pastures. Ewe bodyweight gains were greater at low than at high stocking rate and were not affected by the parasite control treatments; differences in breech soiling and fly strike were similar to those in the lambs. Most importantly the parasite treatment produced a highly significant effect on ewe fleece weight at weaning. Ewes drenched and lambing on the safe pastures produced an extra 0.43 kg of wool, calculated to represent an increase of at least 40% during this period at the low-level of parasitic infection.  相似文献   

4.
OBJECTIVE: To describe the occurrence of blowfly strike in sheep flocks in two shires located in south-eastern Queensland. DESIGN: Postal survey of woolgrowers within Stanthorpe and Inglewood shires. PROCEDURE: Questionnaire posted to woolgrowers in June 1999 seeking information on the monthly occurrence of flystrike and number of sheep at risk. RESULTS: Incidence of body strike and breech strike between August 1998 and May 1999 was 1.1 and 0.5%, respectively. The highest incidence of body strike and breech strike was reported in lambs (6.1%) and weaner sheep (1.5%), respectively. The seasonality of the incidence of body strike was bimodal (November and February), whereas the seasonality of the incidence of breech strike was unimodal (April). Occurrence of body strike within a 3-month period in flocks located within 40 to 50 km of each other was significantly (P < 0.05) clustered. CONCLUSION: Body strike appears to be more common than breech strike in the study area, mainly affects lambs and weaners and high-risk periods occur during late spring and autumn. Study results provide valuable information for planning blowfly strike control programs in the area such as timing of management procedures, use of fly traps), and enable the economic impact of flystrike on the industry in this area to be assessed.  相似文献   

5.
Objective To investigate the efficacy of ivermectin in an intraruminal controlled-release capsule (CRC) against blowfly strike.
Design Pen and field trials with controls.
Animals Pen studies: Two breech strike trials involving 60 Romney and 60 Merino sheep. One body strike trial using 100 Merino sheep.
Field trials: Eight trials in New Zealand used 1000 Romney and Romney-cross sheep. Fifty Merino lambs in one trial in Australia.
Procedure Pen studies: Sheep were allocated to two equal groups. One was not treated, the other sheep received a CRC that delivered ivermectin at 20 μg/kg/day for 100 days. In the breech strike trials, each animal was given an oral laxative 2 days before exposure to adult Lucilia cuprina . In the body-strike trial, the sheep sheep were kept wet to increase susceptibility prior to the release of blowflies.
Field trials: Fifty or 200 sheep allocated to equal groups of nontreated or treated with the CRC and grazed at pasture exposed to natural blowfly challenge.
Results Pen studies: Breech strikes developed in 24 of 60 controls but in none of 60 CRC-treated sheep. There was a 35% reduction in the number of CRC-treated sheep struck on the body.
Field trials: The average number of breech strikes in CRC-treated sheep was reduced by 86% (P < 0.001). The number of body strikes in the treated groups was a reduced by 27% (P < 0.05).
Conclusion The ivermectin CRC is a useful aid in controlling breech strike, but provides only moderate reduction in the incidence of body strike.  相似文献   

6.
An effort was undertaken to replace a community of sheep endoparasites that had been classified as resistant to levamisole and albendazole with a community of more susceptible parasites using a dilution approach that could be integrated into the management of a commercial flock. For this study, pastures on this sheep farm were divided into two areas: north and south. Strategically timed anthelmintic treatments combined with pasture management reduced to nondetectable levels the endemic community of anthelmintic resistant parasites in this flock and on these pastures by early summer. A group of 102 ewes, lambs, and rams were experimentally infected with third stage larvae from the more susceptible community of parasites. These sheep then seeded the south pastures with the new parasite community, while sheep on the north pastures maintained the endemic resistant community. Despite its insensitivity as a technique for detecting anthelmintic resistance, fecal egg count reduction tests at the end of the grazing season indicated that the more susceptible parasites were present on the south pastures while resistant parasites were present on the north.The following grazing season, similar protocols were used to introduce the more susceptible parasites onto the north pastures. At the end of the grazing season, fecal egg count reduction tests indicated that the new community of parasites had become established on both groups of pastures of the farm.  相似文献   

7.
Objective To compare the prevalence of breech flystrike (‘breech‐strike’) on 12–20‐month‐old Merino hoggets that were mulesed, had breech and tail clips applied (‘clipped’) or were left unmulesed but treated strategically with long‐acting insecticide. Design A cohort study on three farms in southern Victoria. Methods Three treatment groups were established at lamb marking on each farm. The unmulesed group was treated with dicyclanil when 12 months old in September or October (‘early‐season treatment’). The prevalence of breech‐strike and key risk factors, including soiling of the breech with faeces (‘dag’) and urine (‘stain’), and breech wrinkle, were compared between the groups. Results Over all the farms, breech‐strike occurred on 1.1% of mulesed sheep and 7.7% of clipped sheep. Clipped sheep had a relative risk of breech‐strike of 18.2‐, 16.8‐ and 3.0‐fold that of mulesed sheep on the three farms. Unmulesed sheep treated with dicyclanil had a similar prevalence of breech‐strike to that of mulesed sheep (overall 0.9%, range 0–2.5%), but had significantly more dag, stain and wrinkle. Conclusion Early‐season treatment of unmulesed sheep prevented most breech‐strikes during the spring and early summer, and offers a short‐ to medium‐term option for the control of breech‐strike in south‐eastern Australia. There were some benefits associated with using clips, namely less dag and stain, and a shorter time spent crutching. However, to control breech‐strike the clipped sheep should be treated the same as unmulesed sheep. Reducing the prevalence and severity of dag will be a major component of strategies to control breech‐strike of Merinos in this region.  相似文献   

8.
The use of a time-space scan statistic--defined by a cylindrical window with a circular geographic base and height corresponding to time--was investigated as a method of detecting clustering in veterinary epidemiology whilst controlling confounding. The example data set consisted of farmer-recorded occurrence of body strike and breech strike between August 1998 and May 1999 in 26 sheep flocks located in two local government areas of southeastern Queensland, Australia. This information was derived from a questionnaire survey mailed to farmers. Potentially confounding factors included in the investigation were flock size (< or = median, > median), flock structure (proportion of lambs, wethers, ewes and rams), pesticide application for flystrike control (yes, no) and rainfall (< or = median, > median). The total sheep population within selected flocks was 92,660; 1012 (1.09%) and 518 (0.56%) cases of body strike and breech strike were reported in 16 and 10 flocks, respectively.Clustering analyses of body strike and breech strike were undertaken separately, because different predisposing factors are associated with these diseases. Significant clustering of body strike (28.76 degrees S, 151.82 degrees E) during March 1999 and breech strike (28.73 degrees S, 151.16 degrees E) between February and May 1999 was detected. Adjusting for flock structure, flock size, pesticide use and rainfall did not alter the most likely cluster of body strike identified--although the relative risk changed (> 10%) after adjusting for flock structure. Adjustment for flock structure and rainfall resulted in different clusters of breech strike being identified.  相似文献   

9.
BACKGROUND AND OBJECTIVE: A hypersensitive inflammatory response, associated with the ingestion of trichostrongylid larvae, is a major cause of diarrhoea and soiling of the breech with faeces in adult Merino sheep ('hypersensitivity scours'). This response is characterised by an infiltration of eosinophils and altered lymphocyte populations in the gut of affected sheep. The objective of this study was to investigate the numbers of Ostertagia circumcincta and Trichostrongylus vitrinus infective larvae that were needed to induce diarrhoea in adult Merino sheep grazing improved pastures. METHOD: Sheep from three farms were categorised as either being susceptible, or not susceptible, to hypersensitivity scours, then transported to an experimental farm and grazed on pastures with low numbers of trichostrongylid infective larvae. They were ranked by farm of origin and previous worm egg count, then systematically allocated to one of five dose-rate groups and infected with 0, 2, 4, 10 or 20 x 10(3) trichostrongylid infective larvae per week for 13 weeks. RESULTS: In sheep selected as being susceptible to hypersensitivity scours, the lowest dose rate of infective larvae (2000 per week) was as effective in inducing diarrhoea as the highest dose rate (20,000 per week). In contrast, even the highest larval dose did not induce diarrhoea in sheep selected as not susceptible to hypersensitivity scours. Sheep selected with an increased susceptibility to hypersensitivity scours also had a significantly higher amount of moisture in their faeces at all times except during summer. CONCLUSIONS: The apparent lack of a threshold dose of trichostrongylid infective larvae needed to induce hypersensitivity scours suggests that even improved worm control programs, which substantially decrease the ingestion of larvae, may not be able to reduce the prevalence of hypersensitivity scours or the severity of breech soiling. Controlled-release anthelmintic capsules will control breech soiling but are often not a cost-effective strategy. Thus, genetic selection of less susceptible sheep is probably the best long-term option for the control of hypersensitivity scours, and the assessment of faecal moisture may be a convenient marker of susceptibility to this syndrome.  相似文献   

10.
Ten field trials were conducted in the North and South Islands of New Zealand to evaluate the anthelmintic efficacy and production responses attributable to treatment of weaner lambs with an intra-ruminal controlled-release capsule formulation of ivermectin. A total of 800 Coopworth, Perendale and Romney lambs weighing on average 20.8-34.8 kg were used. Lambs were either untreated or treated shortly after weaning with an ivermectin controlled-release capsule which delivers ivermectin at 0.8 mg per day for 100 days (minimum dose rate 20 microg/kg/day). Bodyweights, faecal nematode egg counts and dag scores (assessment of faecal soiling in the breech area) were determined before treatment and at about 4,8, 12, 14 and 16 weeks after treatment. Sheep treated with the Ivermectin capsule gained significantly more weight (11.6 kg) over the 16 weeks of the trials compared to untreated sheep (7.3 kg) (p < 0.01). Before treatment, faecal strongylid and Nematodirus spp. egg counts were equivalent (p > 0.10) but, at each time point thereafter, egg counts in ivermectin capsule-treated sheep were significantly lower (p < 0.01 or p < 0.05). Dag scores were not different at the start of the trial (p > 0.10), but at the end of the trial control sheep had significantly greater dags (p < 0.05) than sheep treated with the ivermectin capsule. These findings indicate that treated animals contributed significantly fewer nematode eggs to the contamination of pasture and therefore pasture contamination should be significantly reduced for at least 112 days. The productivity of the ivermectin capsule-treated sheep over the I6 weeks of the trials was also significantly increased compared to salvage-treated controls. Furthermore, the presence of dags, which predispose sheep to blowfly strike in the breech area and result in production losses due to the costs of dagging and downgrading of breech wool, were also significantly (p < 0.05) reduced in the ivermectin capsule-treated sheep.  相似文献   

11.
The selenium nutrition of sheep throughout Victoria was assessed by a survey of the blood glutathione peroxidase activity in 708 flocks. It was shown that the blood glutathione peroxidase activity in sheep had a seasonal variation with lowest levels in the spring. The enzyme activity was correlated with the blood selenium concentration. Areas where blood selenium was less than 0.03 μg/ml in spring were defined. Sheep with low selenium nutrition were grazing pastures in the high rainfall areas on acid soils, particularly those derived from granite.
Selenium concentrations in pasture samples examined were greater than 0.02 mg/kg, and it was found that superphosphate application had no significant effect on the selenium content of pasture. However, management practices such as high stocking rates and rates of application of superphosphate to pasture were associated with low blood glutathione peroxidase activities in sheep.
It was concluded that the selenium nutrition of most of the sheep flocks in Victoria is adequate, and that the deficient areas are localised. There seems little requirement for supplementation of adult sheep. As the delayed type of white muscle disease in spring lambs appears to be the main selenium-responsive disorder, direct supplementation of lambs in the low selenium areas would be the most effective method of ensuring adequate selenium nutrition.  相似文献   

12.
Micro-anatomical differences in skin structure associated with resistance and susceptibility of sheep to fleece-rot and body strike were identified, and found to be of similar magnitude in 2 genetically divergent flocks of medium-woolled Merino ewes. Susceptible sheep were characterised by smaller follicle groups, resulting in higher densities of follicle populations with greater concentrations of the primary follicles (and sudoriferous glands) than in the resistant sheep. From these smaller follicle groups of susceptible sheep, thicker wool fibres grew than were found in the resistant sheep.
The significance of these findings is discussed in relation to the pathogenesis of fleece-rot and body strike of sheep, and the value of the measured skin characters as a method for identifying resistant sheep.  相似文献   

13.
SUMMARY: The productivity of Merino ewes treated with ivermectin and a controlled-release capsule containing albendazole was compared with untreated ewes grazing the same pastures on each of 3 farms. Treated breeding ewes had significantly increased greasy fleece weights (GFW, 6.5% and 7.1%) compared with untreated breeding ewes, on 2 of 3 farms but treatment caused no significant increase in the GFW of non-breeding ewes. Other benefits of treatment on all farms were a significant increase in body weight gain (from 1.7 to 3.7 kg) and a significant decrease in the weight of dag removed at crutching (from 42 to 622 g). These benefits occurred despite the presence on each farm of worms resistant to benzimidazoles. One disadvantage of treatment was an increase in mean fibre diameter of wool from treated ewes of from 0.12 to 0.41 μm. This increase reduces the value of the wool. Partial budgets indicated a net loss of from 8 to 62 cents per ewe for treatment. However, potential benefits such as increased growth rate and wool production from lambs of treated ewes were not included in the analysis. On one farm ewes were classified as ‘susceptible’ to severe dag if they had a dag score ≥ 4 at the time of capsule treatment. Ewes classified as ‘susceptible’ were about 7 times more likely to develop severe dag than were other ewes. There was no significant difference between the GFW of untreated ‘susceptible’ ewes and untreated ewes not classified as ‘susceptible’. Additionally, the response of GFW to treatment was no different to the response seen in ewes that were not classified as ‘susceptible’. The direct cost of diarrhoea and dag formation in Merino ewes was estimated to be 18, 30, 53, 86, 98 and 145 cents per head for ewes with a dag score of 0, 1, 2, 3, 4 and 5, respectively. This cost did not include potential benefits from reduced risk of breech strike, or intangible benefits associated with the improved welfare of sheep.  相似文献   

14.
The pre-weaning production of ewes and lambs in spring on pastures grazed during the previous autumn and early winter by either weaner sheep, adult sheep, or cattle was investigated together with estimating the benefits of pre- and post-lambing drenches to ewes. These treatments were compared with one in which parasitism was uncontrolled in ewes lambing on pastures grazed previously by untreated weaner sheep, and another where parasitism was suppressed by 2-weekly drenching of the weaner sheep and also of the ewes and their lambs. Prior grazing by cattle effectively eliminated infection of pastures with intestinal Trichostrongylus and Nematodirus spp, but less so for Ostertagia spp. Worthwhile reductions in contamination were also achieved by grazing by adult sheep compared with grazing by undrenched weaners. Despite differences in the parasitological status of the pastures, there were no indications that pre-weaning growth rates of lambs were affected. However, wool growth in ewes was reduced by 10 to 20% by parasite infection. Wool growth of ewes on pastures grazed by cattle during the pre-experimental period exceeded that on any other treatment, and was significantly greater than that of ewes on pastures grazed by undrenched weaners. There was no production benefit in giving a pre-lambing drench to ewes on plots contaminated by weaners, or in giving the additional post-lambing drench to ewes grazing on plots contaminated by weaners, adult sheep or cattle.  相似文献   

15.
Toxoplasmosis was thought to be a minor problem on a lowland sheep farm purchasing some 200 ewe lambs annually. Serological investigations and production records suggested a more substantial problem with most of the ewe lambs seroconverting during their first pregnancy, many while still at grass and receiving no supplementary food. Only 60 live lambs were produced per 100 ewe lambs tupped. It was known that cats occasionally inhabited the sheep houses, from which straw bedding was spread onto the pastures after lambing. Trials over two years with ewe lambs grazing either 'clean' or 'dirty' pastures indicated that the straw bedding was the most likely source of infection. Serial serological studies not only defined the time of infection but also showed that the ewe lambs could be kept free of infection and produce more live lambs; 58 live births came from 81 'clean' ewe lambs compared with 21 from 50 'dirty' ewe lambs.  相似文献   

16.
Objective   To test strategies for the application of dicyclanil and mid-season crutching to maximise protection of unmulesed sheep against breech strike.
Procedure   Three hundred and eighty unmulesed Merino weaners were randomly allocated to four groups either left untreated or treated by different strategies with 50 g/L dicyclanil. Treatments included breech treatment alone and breech plus body treatment, with two application times, immediately after shearing and 6 weeks after crutching or shearing. To assess protection, larval implants with newly hatched Lucilia cuprina larvae were applied to 10 different sheep from each group at 3, 4, 5 and 6 months after crutching and shearing and assessed for the development of strike at 48 hours. The concentration of dicyclanil was measured in wool samples clipped from the breeches of the test sheep.
Results   All dicyclanil treatments gave significant reduction in strike in comparison to controls up until 4 months after crutching but protection in the sheep treated immediately after shearing had waned at 5 months. Treating at 6 weeks after crutching provided significant reduction ( P < 0.05) in strike for 6 months. Results for strike incidence immediately after shearing and concentration of dicyclanil in the breech wool also suggested improvements in protection by delaying treatment for 6 weeks.
Conclusion   In most environments it should be possible to protect unmulesed sheep against breech strike with a carefully planned integrated control program incorporating strategically timed crutching, shearing and dicyclanil application. Delaying treatment with dicyclanil to at least 6 weeks after shearing or crutching increased the protection provided in comparison to treatment immediately after shearing.  相似文献   

17.
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.  相似文献   

18.
Three paddocks were contaminated with Haemonchus contortus eggs from early spring to mid summer by yearling sheep. In Paddock 1, all contamination was derived from worms that had been previously inhibited in their development. The contamination in Paddock 2 was produced only by infections recently acquired from pasture, and in Paddock 3 contamination was attributable to both sources. When the yearling sheep were replaced in mid-summer by newly weaned lambs, severe outbreaks of haemonchosis occurred on all paddocks. It was concluded that inhibited H. contortus larvae are capable of producing sufficient eggs, when they resume development, to initiate an outbreak of haemonchosis in susceptible sheep.  相似文献   

19.
A three-year survey (1997-99) was carried out on organically reared sheep flocks throughout Sweden. The aim was to determine the prevalence and intensity of nematode infections and to establish relationships between sheep management practices and parasite infections. Faecal samples from ewes and lambs were collected from 152 organic flocks around lambing-time and during the grazing-period for analysis. Results were compared with the different management practices that farmers use to prevent parasitism in their flocks. A high proportion of the flocks was infected with nematodes. The most prevalent species were Haemonchus contortus, Teladorsagia circumeincta, Trichostrongylus axei. T. colubriformis and Chabertia ovina and infections progressively increased during summer in lambs grazing on permanent pastures. Severity of parasitic infection in lambs was highly dependent on egg output from the ewes. H. contortus was found in 37% of the flocks, even at latitudes approximating the Polar Circle. Nematodirus battus was recorded for the first time in Sweden during the course of this study. Lambs turned out onto permanent pasture showed higher nematode faecal egg counts (epg) than lambs that had grazed on pastures, which had not carried sheep the previous year. This beneficial effect of lambs grazing non-infected pastures persisted if the ewes were treated with an anthelmintic before turn-out and if the lambs were kept on pastures of low infectivity after weaning. In lambs, the prevalence and the magnitude of their egg counts were higher during autumn in flocks where lambs were slaughtered after 8 months of age, compared with flocks where all lambs were slaughtered before this age. These results will be used in providing advice to farmers of ways to modify their flock management in order to minimise the use of anthelmintics, but at the same time efficiently produce prime lambs.  相似文献   

20.
SUMMARY Seventeen trials involving 5737 sheep were conducted to test the efficacy of ivermectin jetting fluid (30 ppm in water) for the control of blowfly strike when applied to sheep either by standard hand jetting or through an automatic jetting race. Sheep were observed for up to 14 weeks after treatment and all strikes recorded. The level of fly challenge varied between trials, resulting in strike rates in untreated sheep ranging between 0 and 94%. At 12 weeks after treatment there were 93% fewer strikes in hand jetted sheep and 84% fewer strikes in machine jetted sheep when compared with untreated sheep. At this time point there was a 90%, 86% and 93% reduction in poll, body and breech strikes, respectively, when hand jetting was used, whereas machine jetting reduced poll, body, breech and pizzle strikes by 84%, 81%, 79% and 100%, respectively.  相似文献   

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