Open Access
Genet. Sel. Evol.
Volume 39, Number 4, July-August 2007
Page(s) 405 - 419
Published online 06 July 2007
Genet. Sel. Evol. 39 (2007) 405-419
DOI: 10.1051/gse:2007011

Genetic and environmental effects on semen traits in Lacaune and Manech tête rousse AI rams

Ingrid Davida, Xavier Druartb, Gilles Lagriffoulc, Eduardo Manfredia, Christèle Robert-Graniéa and Loys Bodina

a  Station d'amélioration génétique des animaux, INRA, UR631, BP 52627, 31320 Castanet-Tolosan Cedex, France
b  Physiologie de la reproduction et des comportements, INRA - CNRS UMR1291, 37380 Nouzilly, France
c  Institut de l'Élevage, ANIO, BP 42118, 31320 Castanet-Tolosan Cedex, France

(Received 4 May 2006; accepted 22 February 2007; published online 6 July 2007)

Abstract - Data from 51 107 and 11 839 ejaculates collected on rams of the "Lacaune" and "Manech tête rousse" breeds, respectively, were analysed to determine environmental and genetic factors affecting semen production traits (ejaculate volume, semen concentration, number of spermatozoa and motility) in young ($\leqslant $ 1 year) and adult ($\geqslant $ 2 years) rams. Fixed effects and variance components were estimated using multiple trait animal models within each breed. For all traits, the main environmental effects identified were year, season, number of ejaculations, daily variation, interval from previous to current collection and age. Heritability estimates were moderate for volume, concentration and number of spermatozoa (0.12 to 0.33) and lower for motility (0.02 to 0.14). Genetic correlations between ages differed from 1 for all traits (0.14 to 0.90), indicating that semen characteristics corresponded to different traits in young and adult rams. Genetic and phenotypic correlations among traits within age category were globally similar for the different breeds and categories of animals.

Key words: ram / semen / environmental factor

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© INRA, EDP Sciences 2007