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摘要
The objective of this study was to compare four Spanish maternal lines of rabbits (A, V. H and LP) on different criteria but selected for litter size at weaning, since their foundation until present for 39, 35, 16 and 4 generations, respectively. The comparisons among the lines were performed for litter size traits and kindling interval. The first comparison made was at the foundation time of the lines, using mixed animal models (additive and non-additive permanent effects) involving the complete data set (from June 1980 to February 2009) and the full pedigree to take into account the process of selection. A second comparison was made at fixed times and location (during the six year-seasons shared at the same farm and similar conditions for lines A, V and H involving data from March 1997 to August 1998, and A, V and LP lines from September 2007 to February 2009. The models used in the second comparison did not include the complete data set nor the additive genetic effects so that line comparisons were not dependent on the genetic model. The raw means for 47,132 parities produced from 12,639 does were 9.80, 9.07, 7.79 and 6.95 rabbits for total born, number bon alive, number weaned and number marketed per litter, respectively, demonstrating high levels of prolificacy among the lines, and with a kindling interval of 49.80 days.
At their respective times of foundation, line A showed the lowest litter size with mean differences (1.39 rabbits/litter for total born, 120 for number born alive, 0.84 for number weaned and 1.06 for number marketed) among the combined means of the other lines being important Lines V and H did not show significant differences for litter size traits, but for kindling interval the contrast was 330 +/- 0.72 days, which was significant and favourable to line H. LP exceeded V by approximately one rabbit for all litter size traits. The differences between the lines for kindling interval were negligible. Some interactions between lines and farm-year-seasons were important.
In comparison of lines A. V and H from March 1997 to August 1998. the pattern of the differences between the line A and the others was similar to the one observed at the origin, and the only significant difference was found between lines V and H for the kindling interval (4.62 days in favour of line V). The comparison between the lines A. V and LP from September 2007 to February 2009 showed an approximation in their reproductive performance compared to the differences at the origin. Overall, good agreement was observed between the comparisons of lines for litter size traits at fixed times, using a model without genetic effects and data recorded during the time of comparisons, and the predictions derived from the model with genetic effects. Another point is the importance of the criteria in the sample of founders of lines that were used to determine the initial or starting performance levels. Therefore, it is recommended that commercial rabbit producers utilize line populations selected for the traits of economic interest rather than on a popular breed.
- 出版日期2011-4
