title: Breech-strike on mulesed, clipped and unmulesed Merino ewes and hoggets in south-eastern Australia.
abstract: OBJECTIVE
  Compare breech-strike on Merino ewes and hoggets that were mulesed, had breech and tail clips applied ('clipped') or left unmulesed and treated strategically with long-acting insecticide.
  
  
  METHODS
  A cohort study on two farms in southern Victoria.
  
  
  METHODS
  Three treatment groups were established at lamb marking in 2008 and 2009 on each farm. The unmulesed group was treated with a long-acting insecticide in early spring. The prevalence of breech-strike and key risk factors, including presence of dag, urine stain and breech wrinkle, were compared between groups.
  
  
  RESULTS
  Breech-strike was detected from October to December on 1.9% and 7.2% of mulesed, and on 14.8% and 12.5% of clipped ewes, respectively, on each farm. Thus, clipped ewes had a relative risk of breech-strike 7.8- and 1.7-fold that of mulesed ewes. Unmulesed ewes treated with insecticide had similar or less breech-strike compared with mulesed ewes (3.4% and 1.4%), but significantly more dag, stain and breech wrinkle. From January, breech-strike on unprotected unmulesed ewes was 8.5% and 2.8%, compared with 3.5% and 0% on mulesed ewes.
  
  
  CONCLUSIONS
  Early-season treatment of unmulesed sheep prevented most breech-strikes during spring and early summer on both hoggets and breeding ewes, confirming it as a short- to medium-term option for the control of breech-strike. Some benefits were associated with the use of clips but, to control breech-strike, clipped sheep should be treated the same as unmulesed sheep. Genetic selection to reduce the prevalence of dag will be required for future strategies to control breech-strike on Merino sheep in south-eastern Australia.
authors.affiliation: The Mackinnon Project, University of Melbourne, 250 Princes Hwy, Werribee, Victoria, 3030, Australia. j.larsen@unimelb.edu.au.
authors.forename: L D
authors.initials: LD
authors.lastname: Tyrell
authors.forename: J W A
authors.initials: JW
authors.lastname: Larsen
authors.forename: N
authors.initials: N
authors.lastname: Anderson
mesh_terms: D000818:Animals; D015331:Cohort Studies; D004175:Diptera / Q000469:parasitology*; D005260:Female; D007300:Insect Control / Q000379:methods*; D007306:Insecticides / Q000008:administration & dosage*; D009198:Myiasis / Q000453:epidemiology / Q000469:parasitology / Q000517:prevention & control / Q000662:veterinary*; D015995:Prevalence; D012307:Risk Factors; D012756:Sheep; D012757:Sheep Diseases / Q000453:epidemiology / Q000469:parasitology* / Q000517:prevention & control; D018709:Statistics, Nonparametric; D014739:Victoria / Q000453:epidemiology
chemical_list: D007306:Insecticides
keywords: breech-strike; clips; cyromazine; dag; dicyclanil; flystrike; mulesing