The possible genetic improvement of reproduction and survival rate in Afrino sheep using a threshold model

Author: M.A. Snyman, G.J. Erasmus and J.B. van Wyk
Year: 1998
Issue: 2
Volume: 28
Page: 120 -

The objective of this study was to estimate heritability and breeding values on theunderlying scale for different reproductive traits and survival rate in Afrino sheep to ascertain whether they can be improved by selection on estimated breeding values obtained under a threshold model. Data collected on the Carnarvon Afrino flock over the period 1969 to 1994 were analysed by means of a GFCAT set of programmes. The reproductive traits analysed included fertility (whether a ewe lambed or not; 0 or I), litter size (number of lambs born to a ewe mated; 0, 1, 2 or 3), fecundity (number of lambs born to a ewe that lambed; 1, 2 or 3), number weaned (number of lambs weaned to a ewe mated; 0, 1, 2 or 3) and survival rate from birth to weaning (whether a lamb born alive, was dead or alive at weaning; 0 or 1). Heritabilities on the underlying scale of 0.20, 0.27, 0.42, 0.19 and 0.02 were estimated for the respective traits. The results suggest that reproduction rate, but not survival rate, can be increased in Afrino sheep by selection on breeding values estimated on the underlying scale applying a threshold model.

Keywords: Afrino sheep, reproductive traits, sire evaluatiion, threshold model
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