Genetic analysis of superovulatory response of Holstein cows in Canada

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.

Using genomics to enhance selection of novel traits in North American dairy cattle,

“…In Canada, research has begun on the analysis of the number of total and viable embryos produced per flush for >135,000 flushes from 54,000 cows. Preliminary research indicates heritabilities of 0.14 to 0.17 for these traits as well as significant genetic differences among sires (Jaton et al, 2015). Genomic analysis shows that a few QTL may have a large influence (Jaton et al, 2015).…”

“…Preliminary research indicates heritabilities of 0.14 to 0.17 for these traits as well as significant genetic differences among sires (Jaton et al, 2015). Genomic analysis shows that a few QTL may have a large influence (Jaton et al, 2015). Research is continuing, but no plan has been formulated yet for its application.…”

Symposium review: The choice and collection of new relevant phenotypes for fertility selection

“…In genetic evaluations, if the use of timed AI is not coded or considered in analyses, the selection process might benefit cows that are merely good responders to synchronization protocols (Berry et al, 2016). Relatedly, it has been shown that there is a genetic element to the response of cows to superovulation protocols (Jaton et al, 2016), and therefore it is possible that similar conclusions could be found for synchronization programs. Goodling et al (2005) attempted to examine the effects of reproductive synchronization on genetic parameter estimates for days to first breeding, DO, and pregnancy rate at 120 d postpartum, and found synchronization treatment produced heterogeneous variances.…”

Impact of Type and Dose of Recombinant Human Follicle Stimulating Hormone on Embryos Production in Dairy Cows and Their Relationship with AMH Concentration

“…The vast variability in the ovarian response and subsequent embryos production in MOET programs are related to many factors includes gonadotrophin sources and preparation [5][6][7][8][9], super-stimulation protocol [10], follicular population and its dynamics growth at the time of treatment initiation [23,24], farm management [25], nutritional status [26,27], genetic merit for fertility traits [28][29][30] and environmental conditions [31]. It has been demonstrated that FSH:LH ratio affects the ability of the ovary to respond to exogenous gonadotrophin treatment [4].…”