Jm. Brun et F. Lebas, INTERACTIONS OF SIRE AND FEED COMPOSITION ON THE REPRODUCTIVE PERFORMANCES OF BREEDING DOES, Annales de zootechnie, 46(4), 1997, pp. 297-308
Reproductive performances of 225 cross-bred rabbit does 'Inra 1067', s
hed by 15 bucks of the A2066 strain mated to A1077 does were studied o
ver I year. These does were fed isoenergetic diets containing 14.9% (B
) or 21.6% (H) crude protein on dry matter basis. The diet did not inf
luence litter size at birth or at weaning but individual weaning weigh
t and hence litter weight were increased with diet H by 8.2 and 6.5% r
espectively. The interaction between sire and feed was investigated at
two levels: 1) the structure of genetic variability within each feedi
ng and particularly the part of does sire component of variance (which
product by 4 is the cross-bred heritability in the strain A2066); and
2) the genetic correlation due to paternal genes between the expressi
ons of the same traits in the two feedings, considered as two differen
t traits. For litter size (total born alive, weaned) and litter weight
at weaning, the sire part of variance was near zero with diet B leadi
ng to an heritability of 0.05 on average over these four traits, where
as the latter parameter was 0.42 with diet ii. The individual weaning
weight on the contrary, gave the same pattern of variability with both
diets, with a similar heritability of about 0.14. The estimates of ge
netic correlations between the expressions of the same trait in the tw
o diets were quite unaccurate, varying between -0.1 and + 1, the true
value being likely low, about 0.4, for numerical productivity related
traits. According to the proteic level of the feed, the expression of
reproductive traits might involve partly different sets of genes.