This study was conducted in four Spanish maternal lines of rabbits (A,
V, H and LP) reared in the closed nucleus of selection located in the farm of
the Department of Animal Science, Polytechnic University of Valencia. Data
for this study were collected during the program of selection of maternal lines
of rabbits from September 1980 to March 2011. The main objective of this work was to compare the longevity trait in four maternal lines of rabbits (A, V, H and LP) selected for litter size at weaning but founded on different criteria. The comparison has been done at their foundation time using the complete pedigree file and the complete data set performed from their foundation until March, 2011. The second objective of this study was to compare the lines at fixed times. The fixed times of comparison were from March, 1997 to September 1998 for A, V and H lines, and from September, 2009 to March, 2011 for A, V and LP lines. The results of the present study could be summarized as follows:
1- The estimated additive genetic variance of longevity resulted from the use
of the complete data set (12693 does and 14805 record in the pedigree file),
and the complete genetic model was 0.195 with standard deviation of 0.03.
This estimate corresponds to an effective heritability of 0.163, while
corresponds to an equivalent heritability of 0.104 considering the proportion
of uncensored data as 59.57 % of the whole data set.
2- Regarding the comparison of longevity between the lines A, V, H, and LP
at their foundation using the complete genetic model and the complete data
set from the foundation of the four lines until March, 2011. The lines V, H
and LP showed a significant superiority over line A. The greatest difference
was between the lines A and LP, while the differences between line V and
both of H and LP lines were small and non significant. These differences
between lines may be attributed to the history of foundation of each line where all of them were founded on different criteria but all selected for litter
size at weaning.
3- Regarding the comparison between lines at fixed times, the first comparison was between lines A, V, and H and the selected data were performed during the period from March, 1997 to September, 1998. It is shown that line A had a risk of culling or death greater than lines V and H. the same trend as in the case of the comparison at the foundation time of these lines, while the differences between lines V and H were non significant. The second comparison was between lines A, V, and LP and the selected data set were performed during the period from September, 2009 to March, 2011. This comparison reflects the current situation of these three lines, it is shown the inferiority of the line A over the two other lines (the same trend as the anterior comparison), this means lower longevity of line A which had limited capacity to face the opposite risk factors. No significant difference between the V and LP lines has been founded.
4- The observed differences between lines during these periods were much
lower than those at the foundation time due to in part to the main cause of
these differences in the genetic level of the contemporary animals compared
to the founders.
- Given the expected differences between lines at the two fixed times that
computed using the complete genetic model (which included the additive
genetic value of animals), showing that the observed and expected values of
the hazard are relatively similar. This means that the complete model used
in the analysis was suitable to describe this longevity data set. |
