Genet. Sel. Evol.
Volume 33, Number 3, May-June 2001
|Page(s)||249 - 271|
Genet. Sel. Evol. 33 (2001) 249-271
Genetic components of litter size variability in sheepMagali SanCristobal-Gaudya, Loys Bodinb, Jean-Michel Elsenb and Claude Chevaleta
a Laboratoire de génétique cellulaire, Institut national de la recherche agronomique, BP 27, 31326 Castanet-Tolosan, France
b Station d'amélioration génétique des animaux, Institut national de la recherche agronomique, BP 27, 31326 Castanet-Tolosan, France
(Received 6 June 2000; accepted 11 December 2000)
Classical selection for increasing prolificacy in sheep leads to a concomitant increase in its variability, even though the objective of the breeder is to maximise the frequency of an intermediate litter size rather than the frequency of high litter sizes. For instance, in the Lacaune sheep breed raised in semi-intensive conditions, ewes lambing twins represent the economic optimum. Data for this breed, obtained from the national recording scheme, were analysed. Variance components were estimated in an infinitesimal model involving genes controlling the mean level as well as its environmental variability. Large heritability was found for the mean prolificacy, but a high potential for increasing the percentage of twins at lambing while reducing the environmental variability of prolificacy is also suspected. Quantification of the response to such a canalising selection was achieved.
Key words: canalising selection / threshold trait / heterogeneous variances / litter size / sheep
Correspondence and reprints: Magali SanCristobal-Gaudy
© INRA, EDP Sciences 2001