Abstract
The aim of this work was to evaluate the
response in 10 generations of selection for ovulation
rate in rabbits using a cryopreserved control population.
Selection was based on the phenotypic value of ovulation
rate estimated at d 12 of second gestation by laparoscopy.
To produce the control population, embryos
from 50 donor females and 18 males, belonging to the
base generation of the line selected for ovulation rate,
were recovered. A total of 467 embryos (72-h embryos)
were vitrifi ed and stored in liquid N2 for 10 generations.
The size of both populations was approximately 10
males and 50 females. The number of records used to
analyze the different traits ranged from 99 to 340. Data
were analyzed using Bayesian methodology. A difference
between the selected and the control populations
of 2.1 ova (highest posterior density interval (HPD95%)
[1.3, 2.9]) was observed in ovulation rate (OR), but it
was not accompanied by a correlated response in litter
size (LS; −0.3; HPD95% [−1.1, 0.5]). The number
of implanted embryos (IE) increased with selection in
1.0 embryo (HPD95% [−0.6, 2.0]), but this increase was
not relevant. Prenatal survival, embryonic survival, and
fetal survival (FS) were calculated as LS/OR, IE/OR,
and LS/IE, respectively. Prenatal survival was reduced
with selection (−0.12; HPD95% [−0.20, −0.04]), basically
because of a decrease in FS (−0.12; HPD95%
[−0.19, −0.06]). Embryonic survival could have slightly
decreased (−0.05; HPD95% [−0.12, 0.02]). In summary,
comparison with a control population showed that ovulation
rate in rabbits increased with selection without
any correlated response in litter size, basically because
of a decrease in fetal survival.
