title: Prevalence of breech-strike in mulesed, clipped and unmulesed Merino hoggets in south-eastern Australia.
abstract: 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.
  
  
  METHODS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: The Mackinnon Project, University of Melbourne, 250 Princes Hwy., Werribee, Victoria 3030, Australia. j.larsen@unimelb.edu.au
authors.forename: J W A
authors.initials: JW
authors.lastname: Larsen
authors.forename: L D
authors.initials: LD
authors.lastname: Tyrell
authors.forename: N
authors.initials: N
authors.lastname: Anderson
mesh_terms: D000822:Animal Husbandry / Q000379:methods*; D000818:Animals; D015331:Cohort Studies; D004175:Diptera; D005260:Female; D007300:Insect Control / Q000379:methods*; D007605:Juvenile Hormones / Q000008:administration & dosage; D008297:Male; D009198:Myiasis / Q000453:epidemiology / Q000517:prevention & control / Q000662:veterinary*; D015995:Prevalence; D012621:Seasons; D012756:Sheep; D012757:Sheep Diseases / Q000453:epidemiology* / Q000517:prevention & control; D013623:Tail / Q000601:surgery; D014739:Victoria / Q000453:epidemiology; D014935:Wool
chemical_list: D007605:Juvenile Hormones; C121718:dicyclanil