Abstract #T46

# T46
Genetic and genomic analysis for oocyte number and embryo production traits in Holstein cattle using in vitro fertilization data.
C. Sun*1, D. Kendall1, C. Heuer1, J. Deeb1, R. Vishwanath1, M. Fosado1, J. Moreno1, 1ST Genetics, Navasota, TX.

The modern reproduction technologies ovum-pickup (OPU) and in vitro fertilization (IVF), combined with genomic selection provide a rapid and sustainable route for genetic improvement in both efficiency and productivity in dairy cattle. The aim of this study was to estimate variance components and identify regions of the genome associated with traits related to oocyte number and embryo production in Holsteins. Data collected on a Holstein dairy farm in Wisconsin from 2013 to 2016 included 11346 OPU and in vitro fertilization records from 1505 unique elite females and 216 unique service bulls. Six traits were defined: number of oocytes collected (NOC), number of oocytes on drop (NOD), number of cleaved embryos (NCE), number of unfertilized oocytes (NUO), number of dead embryos (NDE) and number of transferable embryos (NTE). A univariate repeatability animal model analysis was performed for these traits. Because these are count variables following a Poisson distribution, generalized linear mixed models (GLMM) with a log link function were employed in ASREML. Of the 1505 unique females, 580 were genotyped using a variety of chips. All genotyped animals were imputed to include those markers used for official US genomic evaluations based on a large genotyped population. 58275 SNPs (after quality control) and EBVs from the GLMM models were used for genome-wide association studies by fitting all the SNPs as random effects using a linear mixed model in GCTA. NOC and NOD only depends on a donor’s maternal genetic effect, whereas paternal fertility must be considered for other embryo traits. Estimates of maternal heritability were 0.158 for NOC, 0.134 for NOD, 0.162 for NUO, 0.104 for NCE, 0.175 for NDE, and 0.139 for NTE, whereas the relative genetic impact of the paternal component was small. Estimates of the genetic correlations between the maternal and the paternal component were slightly negative for NUO, NCE and NTE, indicating a genetic antagonism. The p-values of the genome wide association (GWAS) studies showed that several markers exceeded significance thresholds.

Key Words: In vitro fertilization, embryo, variance components