Effects of reproduction, genotype and anthelmintic treatment of ewes on Ostertagia spp. populations

Donald, A.D.; Morley, F. H. W.; Waller, P.J.; Axelsen, A; Dobson, R.J.; Donnelly, J. R.

doi:10.1016/0020-7519(82)90069-8

Cited by 27 publications

(6 citation statements)

References 26 publications

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“…The Merinos in this study tended to have higher WEC than non-Merino ewes (five of eight occasions on Farm 1, and all four occasions on Farm 4). This is consistent with the findings of Donald et al (1982) who noted that, regardless of whether ewes had been treated with an anthelmintic before lambing, first-cross ewes had significantly fewer Teladorsagia spp. adult worms than Merinos (P < 0.001), and their WEC counts after lambing were also much lower.…”

Section: Merinossupporting

confidence: 91%

The effects of parasitism on ewes for prime lamb production in western Victoria

et al. 2021

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Context. Internal parasites are estimated to cost the Australian sheep industry AUD436 million per annum (p.a.). Aims. To assess the effects of parasitism in flocks producing prime lambs in the 500-700 mm p.a rainfall. area of Victoria.Methods. Ewes on two farms that followed 'best practice' gastrointestinal parasite control programs (BP) and two farms that did not (regionally typical, TYP) were compared. Separate cohorts of ewes were monitored from pregnancy scanning to their subsequent joining each year for three consecutive seasons. Observations included worm egg count (WEC), bodyweight, condition score and presence of breech soiling (dag). These were compared between groups that were treated to suppress parasitism (SUP) and those treated according to the usual program used on that farm (NSUP). Data from individual ewes were analysed using a multivariable, mixed-effects regression model. Key results. After adjusting for known confounders, SUP ewes were 1.2 (95% CI 0.80-1.6) kg heavier than NSUP ewes. Mature SUP ewes were significantly heavier than NSUP ewes at their next joining on 6 of 18 occasions, mostly following winters when ewes experienced nutritional stress. Ewe hoggets and Merino ewes were generally more susceptible to parasitism than mature non-Merino ewes; single-bearing ewes were less susceptible than those bearing twins. The effects of parasitism were reduced when peri-parturient ewes had an optimal condition score and grazed adequate pastures.Conclusions. Ewes were more vulnerable to parasitism when immature, twin-bearing, or under nutritional stress. Some of the greatest differences between SUP and NSUP ewes occurred following periods of low feed availability and/or ewe condition score. The difference between the mean bodyweight of SUP and NSUP Merinos was not always greater than that of the non-Merinos. WECs are not a sole reliable indicator of the effects of parasitism in this class of sheep.Implications. Immature or twin-bearing ewes, and those in suboptimal body condition, should be managed considering their increased vulnerability to parasitism, and WEC interpreted alongside other factors. Controlled release capsules were not cost effective in reducing production loss from gastrointestinal nematodes in most years but may be effective in reducing the effects of clinical parasitism in some cases.

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Section: Merinossupporting

confidence: 91%

The effects of parasitism on ewes for prime lamb production in western Victoria

et al. 2021

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“…Periparturient ewes displayed a loss of their acquired immunity to T. circumcincta infection as evidenced by an increase in FEC during late pregnancy and lactation. FEC as an indirect measure of immunity has proven to be an effective criterion with which to assess the extent of PPRI in ewes and it has frequently been used to compare differences in resistance to infection between breeds ( 4 , 5 , 10 , 30 – 33 ) . In the LP treatment, infected G ewes had FEC which were more than five times higher than that of B ewes (Fig.…”

Section: Discussionmentioning

confidence: 99%

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

Zaralis¹,

Tolkamp²,

Houdijk³

et al. 2008

Br J Nutr

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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 £ 2 £ 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.

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“…There has been surprisingly little research into the production of cross-bred animals for enhanced resistance to nematodes although Border Leicesterr Merino sheep are more resistant to nematodes than purebred Merinos (Donald et al 1982). Most research has been done with beef cattle and a variety of breeds have been created by cross-breeding, some of which, such as the Belmont Red, appear to have superior resistance to nematode infection (Mackinnon et al 1991).…”

Section: Cross-breedingmentioning

confidence: 99%

Alternatives to anthelmintics for the control of nematodes in livestock

2006

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Efficient and welfare-friendly livestock production demands the control of nematode infection. Current control measures rely upon anthelmintic treatment but are threatened by the widespread evolution of drug-resistance in parasite populations. Several methods have been advocated to control nematodes without relying on effective anthelmintics. These include grazing management, biological control, nutritional supplementation, vaccination, and genetic approaches. Each method has its advantages and disadvantages. There are several grazing management schemes that can reduce the severity of infection but they are insufficient on their own to control infection. Biological control includes the use of predatory fungi to control nematode populations and the use of pasture species that can reduce the intensity of infection. Fungi can control nematodes but the current requirement for daily feeding means that this approach will be most useful for animals that are handled daily. Feeding supplementary protein can control nematode infection. The method is simple but can be expensive and may not be cost-effective for some marginal enterprises. Genetic approaches include the use of resistant breeds and selective breeding. Some breeds will thrive in conditions that kill animals from other breeds but substitution of resistant breeds is not always feasible. Selective breeding is effective and inexpensive but requires a high level of expertise. The most appropriate method or set of methods to minimize the adverse consequences of nematode infection may vary among farms.

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Effects of reproduction, genotype and anthelmintic treatment of ewes on Ostertagia spp. populations

Cited by 27 publications

References 26 publications

The effects of parasitism on ewes for prime lamb production in western Victoria

The effects of parasitism on ewes for prime lamb production in western Victoria

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

Alternatives to anthelmintics for the control of nematodes in livestock

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