Variation in reproduction and production of Poll Dorset ewes [sheep].
1994
Hall D.G. | Fogarty N.M. | Gilmour A.R.
Poll Dorset ewes were joined to Booroola Merino or Trangie Fertility Merino rams, and there were 1678 individual ewe joinings over 4 years. Litter size averaged 1.37, maternal lamb survival 0.70, and number of lambs weaned per ewe was 0.94. There were large variations in the reproductive traits due to year and stud and lesser effects due to age. Each extra kilogram of ewe liveweight at joining increased litter size by 0.012 and weight of lamb weaned by 0.39 kg, but had no significant effect on maternal lamb survival or number of lamb weaned. Multiple-bearing ewes weaned 0.72 more lambs and 16.2 kg more lamb weight than single-bearing ewes. Greasy fleece weight averaged 2.2 kg per ewe per year and single bearing produced 0.19 kg per ewe more than multiple- bearing ewes. Dystocia caused 53 percent and starvation-mismothering-exposure caused 23 percent of lamb deaths; the proportion of non-dystocia deaths increased with increasing ewe joining liveweight. The large variation between studs in reproductive performance partly reflected genetic differences between Poll Dorset flocks which could be exploited.
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