Factors explaining the incidence of breech strike in a Mediterranean environment in unmulesed and uncrutched Merino sheepJ. C. Greeff A E , L. J. E. Karlsson B , A. C. Schlink C and A. R. Gilmour D
A Department of Agriculture and Food Western Australia, 3 Baron Hay Court, South Perth, WA 6151, Australia.
B RMB 314, Bridgetown, WA 6255, Australia.
C School of Animal Biology, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia.
D 11 Holman Way, Orange, NSW 2800, Australia.
E Corresponding author. Email: email@example.com
Animal Production Science - https://doi.org/10.1071/AN16528
Submitted: 2 August 2016 Accepted: 7 December 2016 Published online: 1 March 2017
Factors responsible for an increase in breech strike were investigated in an unmulesed Merino flock in a Mediterranean environment that were not crutched in 4 years but were crutched in the subsequent 2 years. No chemical preventative treatments such as dipping or jetting were applied in order to assess the susceptibility of the different progeny groups. The number of breech strikes for each animal was recorded from birth to hogget shearing at 17 months of age. Production traits were measured and a large number of visual wool and body conformational traits were subjectively scored to determine whether they contribute to variation in breech strike. Large differences (P < 0.01) in the incidence of breech strike were found between years. A significant interaction (P < 0.05) was found between year of birth and sex for breech strike to weaning, as rams had a higher strike rate than ewes in 1 year only. Across years ewes generally had a higher strike rate than rams. No consistent pattern in potential indicator traits could be found across years, as many traits each explain a small proportion of the variation in breech strike. Dags and skin wrinkle in the tail and breech area contributed most to the variation in breech strike. In uncrutched sheep, dags scored at yearling age for rams, and before hogget shearing for ewes, explained 16% and 10% of the variation in breech strike, respectively, whereas tail wrinkle scored post-weaner shearing explained 21% of the variation in breech strike in both ewes and rams. In sheep that were crutched at yearling age, about 4 months before the normal fly season, tail wrinkle was the most important indicator trait of breech strike in rams, whereas dags at yearling and dags before hogget shearing were the most important indicator traits in ewes. This research confirms that dags and wrinkles are major predisposing factors to breech strike in a Mediterranean environment and that sheep with higher dag and wrinkle scores were consistently more likely to be struck. A large proportion of variation in the incidence of breech strike remains unexplained in uncrutched and unmulesed sheep.
Additional keywords: breech wrinkle, dag, flystrike, tail wrinkle.
ReferencesAshworth JR, Hall R (1994) Responses of the sheep blowflies Lucilia sericata and L. cuprina to odour and the development of semiochemical baits. Medical and Veterinary Entomology 8, 303–309.
| Responses of the sheep blowflies Lucilia sericata and L. cuprina to odour and the development of semiochemical baits.CrossRef | 1:STN:280:DyaK2M7ktlKjtg%3D%3D&md5=4f3302ec6683a96467f40e5a88b1b615CAS |
AWI (2008) ‘Visual sheep scores.’ (Australian Wool Innovations Ltd: Sydney)
Belschner HG (1937) Observations on the fleece rot and body strike in sheep, particularly in regard to their incidence, type of sheep susceptible and economic importance. (New South Wales Department of Agriculture) Science Bulletin No. 54, pp. 61–95.
Brodie B, Gries R, Marins A, Vanlaerhoven S, Gries G (2014) Bimodal cue complex signifies suitable oviposition sites to gravid females of the common green bottle fly. Entomologia Experimentalis et Applicata 153, 114–127.
| Bimodal cue complex signifies suitable oviposition sites to gravid females of the common green bottle fly.CrossRef | 1:CAS:528:DC%2BC2cXhslOks77N&md5=2749acab36ddb4661fe7f3db27b136c4CAS |
Dun RB, Eastoe R (1970) ‘Science and the Merino breeder.’ New South Wales Department of Agriculture. (Government Printer: Sydney)
Edwards NM, Hebart M, Hynd PI (2009) Phenotypic and genotypic analysis of a bare breech trait in Merino sheep as a potential replacement for surgical mulesing. Animal Production Science 49, 56–64.
| Phenotypic and genotypic analysis of a bare breech trait in Merino sheep as a potential replacement for surgical mulesing.CrossRef |
Gilmour AR, Gogel BJ, Cullis BR, Thompson R (2009) ‘ASREML user guide. Release 3.0.’ (VSN International: Hemel Hempstead, UK)
Greeff JC, Cox G (2006) Genetic changes generated within the Katanning Merino Resource Flocks. Australian Journal of Experimental Agriculture 46, 803–808.
| Genetic changes generated within the Katanning Merino Resource Flocks.CrossRef |
Greeff JC, Biggs A, Grewar PW, Crumblin P, Karlsson LJE, Schlink AC, Smith J (2013) Dogs can differentiate between odour from sheep that are resistant or susceptible to breech strike. In ‘Proceedings of the 20th conference of the Association for the Advancement of Animal Breeding and Genetics’, 20–23 October 2013, Napier, New Zealand. pp. 397–400. (Association for the Advancement of Animal Breeding and Genetics) Available at http://www.aaabg.org/aaabghome/AAABG20papers/greeff20397.pdf [Verified 9 February 2017]
Greeff JC, Karlsson LJE, Schlink AC (2014) Identifying indicator traits for breech strike in Merino sheep in a Mediterranean environment. Animal Production Science 54, 125–140.
| Identifying indicator traits for breech strike in Merino sheep in a Mediterranean environment.CrossRef |
James PJ (2006) Genetic alternatives to mulesing and tail docking in sheep: a review. Australian Journal of Experimental Agriculture 46, 1–18.
| Genetic alternatives to mulesing and tail docking in sheep: a review.CrossRef |
Karlsson LJE, Pollott GE, Eady SJ, Bell A, Greeff JC (2004) Relationship between faecal worm egg counts and scouring in Australian Merino sheep. Animal Production in Australia 25, 100–103.
Lloyd J (2012) Tail length in unmulesed Australian Merino sheep. Final project report WP599 for Australian Wool Innovation, June 2012. (Australian Wool Innovation Ltd: Sydney)
MLA (2015) Priority list of endemic diseases for the red meat industries. Final Report of Project B.AHE.001. (Meat and Livestock Australia: Sydney)
Pollott GE, Karlsson LJE, Eady SJ, Greeff JC (2004) Genetic parameters for indicators of host resistance to parasites from weaning to hogget age in Merino sheep. Journal of Animal Science 82, 2852–2864.
| Genetic parameters for indicators of host resistance to parasites from weaning to hogget age in Merino sheep.CrossRef | 1:CAS:528:DC%2BD2cXnvVWlurc%3D&md5=1862f7f541e05234a3307932743f6dc0CAS |
Raadsma HW (2000) Genetic aspects of resistance to ovine cutaneous myiases. In ‘Breeding for disease resistance in farm animals’. (Eds RFE Axford, SC Bishop, FW Nicholas, JB Owen) (CAB International Publishing: Oxon, UK)
Raadsma HW, Rogan IM (1987) Genetic variation in resistance to blowfly strike. In ‘Merino improvement programs in Australia. Proceedings of a national symposium, Leura, New South Wales’. (Ed. BJ McGuirk) pp. 321–340. (Australian Wool Corporation: Melbourne)
Scobie FR, O’Connell DO, Bray A, Cunningham P (2002) Breech strike can be reduced by increased area of naturally bare skin around the perineum of lambs. In ‘Proceedings of the 24th Animal Production Society of Australia’. pp. 201–204. (Australian Society for Animal Production)
Smith J, Brewer H, Dyall T (2009) Heritability and phenotypic correlations for breech strike and breech strike resistance indicators in Merino. In ‘Proceedings of the 18th conference of the Association for the Advancement of Animal Breeding and Genetics’. pp. 334–337. (Association for the Advancement of Animal Breeding and Genetics)
Watts JE (1979) Breech strike in scouring sheep. In ‘National symposium on the sheep blowfly and flystrike in sheep’, 25–27 June 1979. pp. 175–178. (Department of Agriculture: Sydney)
Watts JE, Merritt GC (1981) Body strike in sheep. In ‘Proceedings no. 58. Refresher course for veterinarians’. 10–14 August 1981, The Stephen Roberts Lecture Theatre, University of Sydney. pp. 171–193. (University of Sydney: Sydney)