In a diallel cross between four maternal lines of rabbits, the four maternal lines and
the corresponding crossbred females (does) were evaluated concerning functional
longevity, estimating their crossbreeding components. Sixteen genetic groups were
produced by using four maternal lines of rabbit (A, V, H and LP (L)). The groups
were distributed over 4 Spanish farms. In all farms, the V line was present as the
reference group. A total of 7,211 does’ longevity records were recorded. Using a
Cox proportional hazard model of fixed effects, survival analysis was performed
to study longevity analysing the hazard of death or culling. Does from lines A, H
and V had similar risks of death or of being culled, and they were more susceptible
compared with those from line L. The lowest hazard was associated with L line does.
No significant differences were found between the average of all crosses and the V
line except when comparing the V line to the cross between A and H lines, favouring
the former (1.30 higher risk of replacement for AH animals). Significant differences
between reciprocal crosses were observed between VH and HV, in favour of
HV (0.72 of relative risk of replacement) and between LH and HL, in favour of HL
(0.76 of relative risk). Line V had the highest risk due to the direct genetic effects,
and these differences were significant with the lines H (1.40 of relative risk) and L
(1.43 of relative risk). The differences in maternal genetic effects were small and not
significant except between lines H and V in favour of V line (0.75 of relative risk).
The estimated direct heterosis effects do not always follow the same trend but they
showed the importance of the crossing between specialized lines to produce crossbred
does for intensive meat rabbit production. |
