New Zealand Journal of Agricultural Research abstracts
Economic accounting of numbers of expressions and delays in sheep genetic
improvement
P. R. AMER
AgResearch Invermay
Private Bag 50034
Mosgiel, New Zealand
Abstract Formulae were developed which use discounted
gene-flow principles to help quantify the economic value of genetic superiority
in individual rams or ewes. Modifications allow discrimination among situations
with terminal versus self-replacing ewes and rams and among traits expressed in
ewes or lambs at different ages. Results are presented in terms of discounted
genetic expressions. These can be multiplied by the economic value of a change
in a specific trait when weighting selection indexes or conducting cost-benefit
analyses of breeding strategies. In the base situation, numbers of discounted
genetic expressions were 182 and 232 for lamb slaughter traits from a terminal
sire ram, and from a ram breeding self-replacing ewes, respectively. For annual
ewe traits such as number of lambs born and wool production, numbers of
discounted genetic expressions were 167 and 239 from rams breeding terminal and
self-replacing ewes, respectively. Results of calculations were also shown for
breeding females and for lamb traits at birth and traits expressed by ewe
hoggets and by ewes at culling. The effects of alternative values for variables
used in the formulae were tested using sensitivity analysis.
Keywords gene-flow; discounting; sheep; genetic; benefit-cost
New Zealand Journal of Agricultural Research, 1999, Vol. 42: 325-336
0028-8233/99/4203-0325 $7.00/0 (c) The Royal Society of New Zealand
1999
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