Abstract #M25

# M25
Feed efficiency and reproductive performance are genomically independent in lactating Holstein cows.
E. M. Bart1, M. D. Hanigan1, D. M. Spurlock2, M. J. VandeHaar3, R. R. Cockrum*1, 1Virginia Polytechnic Institute and State University, Blacksburg, VA, 2Iowa State University, Ames, IA, 3Michigan State University, East Lansing, MI.

For residual feed intake (RFI) or dry matter intake (DMI) to be used as indirect measures of feed efficiency for selection, they must not be unfavorably associated with reproduction. Previous research in other livestock species suggests there may be a phenotypic relationship between feed efficiency and reproduction; however, the underlying genomic relationship is unknown. Therefore, we hypothesized that associated variants will be shared between feed efficiency and reproductive traits. The objectives of this study were to (1) identify single nucleotide polymorphisms (SNP) associated with DMI, RFI, and reproductive traits, (2) determine concordant variants among these SNP, and (3) identify the underlying genes of any shared variants. Feed, milk, and reproductive data were collected on lactating Holstein cows (n = 1,513) from Virginia Tech (VT), Iowa State University (ISU), and Michigan State University (MSU). Measurements of feed intake, milk yield, milk composition, and BW were used to calculate RFI. Reproductive performance was measured using number of services (NS), days open (DO), and days to first calving (DFC). Genotypic data were available on 677 cows using the Illumina Bovine SNP50 Beadchip. Markers were filtered by call rate (<0.9), allele number (>2), and minor allele frequency (<0.05), which resulted in 54,734 SNP. Genome-wide association analyses were performed using a multi locus mixed model. Significant variants for RFI (n = 55), DMI (n = 54), DO (n = 65), NS (n = 59), and DFC (n = 54) were identified. There were 3 common variants between RFI and DMI on BTA2 (rs109734679 and rs29010223) and BTA17 (rs41845355). A protein coding gene within the intronic region of PDE1A underlied rs109734679. Previous association studies in beef cattle have also identified PDE1A as associated with RFI. There were no concordant SNP between RFI or DMI with any of the reproductive traits. Though weak, there was a genomic relationship between RFI and DMI. However, both RFI and DMI were genomically independent of reproduction. Overall, genomic selection for RFI or DMI would not unfavorably impact reproduction.

Key Words: genomic, feed efficiency, reproductive performance