REVISITING Total weaning weight as a selection criterion — ASN Events
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  2. Concurrent 12 - Genetics on the ground II
  3. REVISITING Total weaning weight as a selection criterion

REVISITING Total weaning weight as a selection criterion (#73)

Kim L Bunter 1 , Daniel J Brown 1
  1. Animal Genetics and Breeding Unit, University of New England, Armidale, NSW, Australia
Data from a single prolific Merino flock (N=10705 joining records) recorded over 10 years were used to estimate genetic parameters for annual total weight weaned (TWW), treated as a ewe trait, of ewes which weaned lambs (N=8615) and the accompanying reproductive traits. TWW was the sum of individual weights of weaned lambs to birth ewe. An alternative trait definition included ewes which lambed and lost, which received zero trait values (TWW0, N=9509). Both TWW and TWW0 were lowly heritable (range h2: 0.06-0.11). Most of the phenotypic variation in these traits resulted from variation in the number of lambs weaned. Trait definition significantly influenced both the observable variation in the weaning weight (ewe) traits and their correlations with reproductive traits. We conclude that selection on an index which combines breeding values for reproductive performance and both direct and maternal contributions to weight traits should be considered to improve ewe productivity under dual purpose breeding goals. This index is provided by Sheep Genetics, which also appropriately analyses individual animal reproductive and weight data while accounting for systematic effects and multiple records.
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