Autores UPV
Ragab Ghanem Mohamed Mohamed,
Sánchez Serrano Juan Pablo,
Mínguez Balaguer Carlos,
Vicente Antón José Salvador,
Baselga Izquierdo Manuel
Abstract
A crossbreeding experiment between 4
Spanish maternal lines of rabbits was performed to estimate
crossbreeding effects on litter size components.
The experiment was designed as a complete diallel
cross involving 4 lines selected for litter size at weaning
(A, V, H, and LP [L]) and their 12 simple crosses.
Does from these 16 genetic groups were distributed
among 4 Spanish farms, but only V line was present in
all farms, allowing connectivity of the data. A total of
2,015 does in the third, fourth, or fifth gestations were
subjected to laparoscopy. The recorded traits were ovulation
rate (OR), number of implanted embryos (IE), total
born (TB), embryo survival (ES), foetal survival (FS),
and prenatal survival (PS). The differences in direct
genetic effects, maternal genetic effects, and individual
heterosis between the lines were estimated according to
Dickersons model. Line A was significantly inferior to
lines V and H, whereas line LP was similar to A line,
but for FS and PS, line A showed the best values, followed
by line LP. Comparing crossbred groups to line
V, significant differences were shown favoring crossbred
groups for OR and IE. The crossbred groups presented
high implantation rate, but the foetal survival was lower
than in V line. Important values for commercial production
were presented by some crosses for OR (HV, 1.26
ova), IE (AH, 1.50 embryos; HV, 1.41 embryos), and TB
(AH, 0.82 rabbits; HV, 0.78 rabbits). Relevant and significant
reciprocal effects were found, especially for OR
in all cases except the LV and VL crosses. These differences
become nonsignificant in most of the other traits.
Regarding direct genetic effects, line A presented lower
estimates than the other lines with important values for
OR, but the opposite was observed for FS. The maternal
effects were significant only for some contrasts in OR
and revealed that the LP line was inferior to the others
(1.08 ova compared to the A line, 1.23 compared to the
H line, and 0.38 compared to the V line). In general, high
positive values for heterosis were found in crossbred
does for OR and IE. The crosses, where lines A and H
were involved, showed significant heterosis. The highest
values were obtained by crossing lines A and H (1.18
ova for OR, 1.87 embryos for IE) followed by the cross
between lines H and V. Crosses between line LP and the
other lines had a negative heterosis for FS and PS.
