Increases in breech wrinkles, breech cover and dags have been shown to increase flystrike susceptibility of Merino sheep. At shearing at approximately 320 days of age in 2007, 2008 and 2009, breech wrinkle (1 to 5), dag score (1 to 5) and breech cover (1 to 5) were scored on 736, 806 and 866 yearlings that were the progeny of 31, 38 and 36 sires respectively. It was hypothesised that flystrike would become worse with an increasing score, where 5 indicated a very wrinkly, very daggy or very woolly breech. Fleece weight was recorded at shearing and fleece midside samples were collected and measured for washing yield. Breech wrinkle score (h² = 0.25 ± 0.07), breech cover (h² = 0.33 ± 0.08) and dag score (h² = 0.10 ± 0.04) were found to be heritable. Breech wrinkle score and breech cover were phenotypically (0.39 ± 0.02, P < 0.05) and genetically correlated (0.40 ± 0.16, P < 0.05). Clean fleece weight was heritable (h² = 0.33 ± 0.06) and showed a strong significant negative genetic correlation (-0.52 ± 0.14, P < 0.001) with breech cover. There was no evidence of flystrike during the three years of investigation, but this stud could decrease susceptibility by decreasing breech cover, breech wrinkles and dag score
Proceedings of the New Zealand Society of Animal Production, Volume 72, Christchurch, 192-195, 2012
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