** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** FETAL LOSS IN CATTLE IS ESTIMATED TO RESULT IN LOSSES OF OVER $1 BILLION ANNUALLY, YET LITTLE IS KNOWN ABOUT THE UNDERLYING CAUSES OF THESE ABORTIONS. THE GOAL OF THIS PROPOSAL IS TO IDENTIFY GENOMIC REGIONS ASSOCIATED WITH ABORTION IN HOLSTEIN DAIRY CATTLE AND TO DETERMINE IF BREEDING FOR A DECREASE IN ABORTIONS WOULD NEGATIVELY IMPACT MILKING PERFORMANCE.THE CHARACTERIZATION OF THE GENETIC CAUSES UNDERLYING ABORTION WILL ENHANCE OUR UNDERSTANDING OF THE MECHANISMS OF ABORTION AND FACILITATE REDUCING THE INCIDENCE OF ABORTION IN CATTLE.THIS PROPOSAL EXTENDS OUR PRELIMINARY STUDY THAT IDENTIFIED GENOMIC REGIONS ASSOCIATED WITH FETAL LOSS IN CATTLE. THE SPECIFIC AIMS OF THIS PROPOSAL ARE TO: 1) IDENTIFY AND VALIDATE GENOMIC REGIONS ASSOCIATED WITH FETAL LOSS IN 500 HOLSTEIN HEIFERS (CATTLE THAT ARE PREGNANT WITH THEIR FIRST CALF)AND 500 PRIMIPAROUS COWS (COWS PREGNANT WITH THEIR SECOND CALF) EXPERIENCING A SPONTANEOUS ABORTION (CASES) AND 5000 HEIFERS AND 5000 COWS THAT CALVE AT TERM OR AFTER 260 DAYS OF GESTATION (CONTROLS); 2) CHARACTERIZE THE GENES, GENE REGULATORY REGIONS AND DUPLICATIONS OR DELETIONS OF THE GENOMIC REGIONS; AND 3) IDENTIFY IF SELECTINGFOR REDUCING FETAL LOSS IS UNFAVORABLY CORRELATED WITH PRODUCTION TRAITS.