About 4000 ewes born over 3 years to single sire matings were repeatedly scored for incidence and severity of dags. Dag scores were analysed for evidence of genetic variation and relationship to structural and performance characteristics. Perendales were found to have lowest incidence of dags followed by Booroola x Perendales, Booroola x Romneys and then Romneys and Border Leicester x Romney ewes. There was no relationship between dag score and either wool or body weight characteristics, either within or between breeds. Among progeny of 6 Romney strain, daughters of Ruakura High Fertility rams had substantially lower incidence with little variation among the rest. It is suggested that long-term selection for fertility in this line has reduced incidence of dags through improved utilisation of forage, possibly as a result of resistance to internal parasites. The mean heritability of dag score was 0.31 with a range of 0.13 to 0.60, indicating that selection would be effective in reducing the incidence of dags and their associated costs to farmers.
Proceedings of the New Zealand Society of Animal Production, Volume 43, , 79-82, 1983
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