Production losses in Merino ewes and financial penalties caused by trichostrongylid infections during winter and spring
1995
Larsen, J.W.A. (Victorian Dept. of Agriculture, Ballarat (Australia)) | Vizard, A.L. (Melbourne Univ., Werribee (Australia). Faculty of Veterinary Science) | Anderson, N. (Commonwealth Scientific and Industrial Research Organisation, Parkville (Australia). Div. of Animal Health)
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 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 and a significant decrease in the weight of dag removed at crutching. 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, reducing 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. 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 so classed. The direct costs of diarrhoea and dag formation are estimated; these did not include potential costs of breech strike or intangible costs associated with reduced animal welfare.
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