Volume 99, Issue 5, May 2016, Pages 3612–3623
Abstract
Superovulation
of dairy cattle is frequently used in Canada. The cost of this protocol
is high, and so is the variability of the outcome. Knowing the
superovulatory potential of a donor cow could influence the breeder’s
decision to superovulate it or not. The main objective of this study was
to perform a genetic analysis for superovulatory response of Holstein
cows in Canada using data recorded by Holstein Canada, and to
investigate if these data could be used for genetic evaluation. Data
contained the total number of embryos and the number of viable embryos
from every successful flushing performed across Canada. After editing,
137,446 records of superovulation performed between 1992 and 2014 were
analyzed. A univariate repeatability animal model analysis was performed
for both total number of embryos and number of viable embryos. Because
both data and residuals did not follow a normal distribution, records
were subject to either logarithmic or Anscombe transformation. Using
logarithmic transformation, heritability estimates (SE) of 0.15 (0.01)
and 0.14 (0.01) were found for total number of embryos and number of
viable embryos, respectively. Using Anscombe transformation,
heritability estimates (SE) of 0.17 (0.01) and 0.14 (0.01) were found
for total number of embryos and number of viable embryos, respectively.
The genetic correlation between the 2 traits was estimated at 0.97 using
logarithmic transformation and 0.95 using Anscombe transformation.
Breeding values were estimated for 54,463 cows, and 3,513 sires. Only
estimated breeding values of sires having a reliability higher than 40%
were considered for estimated breeding values correlations with other
routinely evaluated traits. The results showed that selection for a
higher response to superovulation would lead to a slight decrease in
milk production, but an improvement for functional traits, including all
reproduction traits. In all cases, the estimated correlations are
either low or modest. We conclude that genetic selection for increased
superovulatory response in donors is possible; daughters of sires with
high estimated breeding values for superovulatory response will tend to
yield more embryos, whereas the additive effect of service sire seems
not to contribute to the variability of the 2 superovulation traits and
was not significantly correlated with the additive effect of the donor.
Key words
- superovulation;
- embryo production;
- Holstein;
- genetic parameter;
- breeding value
© 2016 American Dairy Science Association®.
