Abstract
The aim of this work was to evaluate
the correlated responses on survival rates after 10 generations
of selection for ovulation rate (OR). Selection
was based on the phenotypic value of ovulation rate
estimated at d 12 of second gestation by laparoscopy.
Traits recorded were litter size (LS), estimated as total
number of rabbits born per litter in up to 5 parities;
OR, estimated as the number of corpora lutea in both
ovaries; the number of implanted embryos (IE), estimated
as the number of implantation sites; the number
of right and left IE (RIE and LIE); ovulatory difference
(OD), defined as the difference between the right and
the left OR, expressed as an absolute value; implantatory
difference (ID), defined as the difference between
RIE and LIE, expressed as an absolute value; embryonic
survival (ES), calculated as IE/OR; fetal survival (FS),
calculated as LS/IE; prenatal survival (PS), calculated
as LS/OR. A total of 1,081 records were used to analyze
ES, and 770 were used to analyze FS and PS. The number
of records used to analyze the other traits ranged
from 1,079 for ID to 3,031 for LS. Data were analyzed
using Bayesian methodology. Genetic parameters of
OR, OD, and LS were estimated in a previous paper.
Estimated heritabilities of IE, ID, ES, FS, and PS were
0.11, 0.03, 0.09, 0.24, and 0.14, respectively. Estimated
repeatabilities of IE, ID, and ES were 0.22, 0.12, and
0.20. Estimated phenotypic correlations of OR with ES,
FS, and PS were −0.07, −0.26, and −0.28, respectively.
Their estimated genetic correlations with FS and PS
were negative (probability of being negative 1.00 and
0.98, respectively). Nothing can be said about the sign
of the genetic correlation between OR and ES. Ovulation
rate was phenotypically uncorrelated with ID.
Their estimated genetic correlation was positive (probability
of being positive 0.91). The genetic correlation
of ID with PS and LS was not accurately estimated.
Phenotypic and genetic correlations between LS and
survival rates were positive (probability of being positive
1.00). In 10 generations of selection, FS decreased
around 1% per generation. No correlated response in
ES was observed. In summary, the decrease in FS in
rabbits selected for OR seemed to be responsible for the
lack of correlated response observed in LS.
