Dairy Genome Project (DGP) BTA2 & 14

We have focused on chromosomes 2 and 14 because we have identified several milk production and female fertility QTLs on these chromosomes. This project is currently underway and additional families and microsatellites are being genotyped. These results were presented at the International Plant and Animal Genome Conference XIV earlier this year (http://www.intl-pag.org/pag/). Below is the abstract.You can download the poster as a pdf file by clicking on the title.

Fine-Mapping of QTL Influencing Milk Production and Female Fertility in Holsteins

Robert D. Schnabel, Erin M. Sellner, Ping Yao, Matthew C. McClure, Natalya S. Morsci, Jae-Woo Kim, Jeremy F. Taylor

A previous genome scan indicated that CDDR sire M-V-14 was segregating for a QTL on BTA2 influencing both milk fat and protein yield and a QTL on BTA14 influencing milk protein percent (Schnabel et al. 2005). Based on these data, three additional families within the M super-family were genotyped for 56 markers on BTA2 and BTA14. Three distinct statistical approaches were used for QTL analysis: 1) Halfsib regression using QTL Express, 2) Full pedigree MCMC analysis using LOKI, and 3) Joint linkage-linkage disequilibrium (LK-LD) analysis using LDVCM. QTL Express indicated that Sire M-V-14 was segregating for two fat yield QTL near positions 41-cM and 121-cM on BTA2.

Joint analysis of all 5 families using LOKI also identified a fat yield QTL (38-cM) and a protein yield QTL (45-cM) in the same region as detected by QTL Express. Sires M-V-14 and M-III-10 are both segregating for a daughter pregnancy rate (DPR) QTL at 41-cM. Haplotype analysis indicates that the DPR increasing allele is in repulsion phase with the fat and protein yield increasing alleles. Sire M-V-14 is segregating for milk yield (31-cM), protein percent (51-cM) and DPR (34-cM) QTL on BTA14. Three additional sires showed evidence of segregation for another milk production QTL near the telomere. LOKI positioned the milk production QTL at 52-cM but failed to detect the milk production QTL near the telomere. LOKI detected the DPR QTL at 36-cM and provided a slightly narrower QTL peak. Joint LK-LD results from LDVCM provide support for the QTL identified in the other analyses.