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**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** INCLUSION OF FERTILITY TRAITS INTO ANIMAL IMPROVEMENT PROGRAMS HELPED INCREASE REPRODUCTIVE PERFORMANCE IN US DAIRIES DURING THE LAST DECADE. HOWEVER, THE SPECIFIC PROCESSES AFFECTED BY FERTILITY-BASED SELECTION REMAIN LARGELY UNEXPLORED. SUCH KNOWLEDGE IS VITAL TO UNDERSTAND THE EFFECTS OF GENETIC SELECTION AND ALLOWS DAIRYMEN TO REFINE REPRODUCTIVE PROGRAMS BASED ON GENOMIC DATA. IN OUR PRELIMINARY STUDIES, WE DEMONSTRATED THAT FERTILITY TRAITS SUCH AS DAUGHTER PREGNANCY RATE IS POSITIVELY ASSOCIATED WITH DURATION OF ESTRUS AND OVERALL ACTIVITY, WHICH IN TURN IS ASSOCIATED WITH INCREASED ESTRUS DETECTION EFFICIENCY AND ACCURACY, REDUCED INTERVAL TO INSEMINATION, AND INCREASED LIKELIHOOD OF PREGNANCY. CONVERSELY, OUR PRELIMINARY DATA SUGGEST THAT SELECTION FOCUSED ON OTHER TRAITS SUCH AS HEIFER CONCEPTION RATE MAY HAVE UNINTENDED CONSEQUENCES ON EXPRESSION OF REPRODUCTIVE BEHAVIOR AND OVERALL REPRODUCTIVE PERFORMANCE. THESE RESULTS HIGHLIGHT THE NEED TO UNDERSTAND HOW FERTILITY-BASED SELECTION AFFECTS SPECIFIC PHYSIOLOGICAL EVENTS, PARTICULARLY IN FACE OF CURRENT PUBLIC SCRUTINY ON BLANKET THERAPIES AND USE OF REPRODUCTIVE HORMONES. WE PROPOSE TO CHARACTERIZE REPRODUCTIVE BEHAVIOR, OVULATORY CAPACITY, HORMONAL PROFILES, AND MARKERS FOR ESTABLISHMENT OF PREGNANCY IN HEIFERS AND COWS WITH DIFFERENT GENETIC MERIT FOR FERTILITY. WE WILL DETERMINE THE ASSOCIATION BETWEEN FERTILITY TRAITS AND RESPONSIVENESS TO ESTRADIOL, LH RELEASE, AND STEROIDOGENIC PATHWAYS. WE WILL CHARACTERIZE ESTRUS BEHAVIOR IN HEIFERS WITH EXTREME DPR AND HCR VALUES FOLLOWING TREATMENT WITH EQUAL MASS OF EXOGENOUS ESTRADIOL - AN APPROACH THAT ADDS TO CURRENT INFORMATION REGARDING ENDOGENOUS CONCENTRATIONS OF STEROID HORMONES. OUR LONG-TERM GOAL IS TO EXPAND THE UNDERSTANDING OF BIOLOGICAL AND PHYSIOLOGICAL MECHANISMS THAT CONTROL REPRODUCTION IN CATTLE, SO THAT BETTER STRATEGIES TO IMPROVE GENETIC GAIN AND MAXIMIZE REPRODUCTIVE EFFICIENCY CAN BE DEVELOPED. THE EXPECTED OUTCOMES FROM THIS PROJECT ARE A CRITICAL STEP TOWARDS SUCH LONG-TERM GOAL AND IT IS LIKELY THAT, IN THE ABSENCE OF SUCH KNOWLEDGE, KEY INTERACTIONS AMONG GENETIC, PHYSIOLOGICAL, AND MANAGEMENT FACTORS WILL BE OVERLOOKED, LIMITING THE PROGRESS OF ANIMAL IMPROVEMENT PROGRAMS AND SUSTAINABILITY OF THE DAIRY INDUSTRY.

$500,000FY2020National Institute of Food and AgricultureUSDA

University Of Florida, Gainesville FL

Investigators

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**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** INCLUSION OF FERTILITY TRAITS INTO ANIMAL IMPROVEMENT PROGRAMS HELPED INCREASE REPRODUCTIVE PERFORMANCE IN US DAIRIES DURING THE LAST DECADE. HOWEVER, THE SPECIFIC PROCESSES AFFECTED BY FERTILITY-BASED SELECTION REMAIN LARGELY UNEXPLORED. SUCH KNOWLEDGE IS VITAL TO UNDERSTAND THE EFFECTS OF GENETIC SELECTION AND ALLOWS DAIRYMEN TO REFINE REPRODUCTIVE PROGRAMS BASED ON GENOMIC DATA. IN OUR PRELIMINARY STUDIES, WE DEMONSTRATED THAT FERTILITY TRAITS SUCH AS DAUGHTER PREGNANCY RATE IS POSITIVELY ASSOCIATED WITH DURATION OF ESTRUS AND OVERALL ACTIVITY, WHICH IN TURN IS ASSOCIATED WITH INCREASED ESTRUS DETECTION EFFICIENCY AND ACCURACY, REDUCED INTERVAL TO INSEMINATION, AND INCREASED LIKELIHOOD OF PREGNANCY. CONVERSELY, OUR PRELIMINARY DATA SUGGEST THAT SELECTION FOCUSED ON OTHER TRAITS SUCH AS HEIFER CONCEPTION RATE MAY HAVE UNINTENDED CONSEQUENCES ON EXPRESSION OF REPRODUCTIVE BEHAVIOR AND OVERALL REPRODUCTIVE PERFORMANCE. THESE RESULTS HIGHLIGHT THE NEED TO UNDERSTAND HOW FERTILITY-BASED SELECTION AFFECTS SPECIFIC PHYSIOLOGICAL EVENTS, PARTICULARLY IN FACE OF CURRENT PUBLIC SCRUTINY ON BLANKET THERAPIES AND USE OF REPRODUCTIVE HORMONES. WE PROPOSE TO CHARACTERIZE REPRODUCTIVE BEHAVIOR, OVULATORY CAPACITY, HORMONAL PROFILES, AND MARKERS FOR ESTABLISHMENT OF PREGNANCY IN HEIFERS AND COWS WITH DIFFERENT GENETIC MERIT FOR FERTILITY. WE WILL DETERMINE THE ASSOCIATION BETWEEN FERTILITY TRAITS AND RESPONSIVENESS TO ESTRADIOL, LH RELEASE, AND STEROIDOGENIC PATHWAYS. WE WILL CHARACTERIZE ESTRUS BEHAVIOR IN HEIFERS WITH EXTREME DPR AND HCR VALUES FOLLOWING TREATMENT WITH EQUAL MASS OF EXOGENOUS ESTRADIOL - AN APPROACH THAT ADDS TO CURRENT INFORMATION REGARDING ENDOGENOUS CONCENTRATIONS OF STEROID HORMONES. OUR LONG-TERM GOAL IS TO EXPAND THE UNDERSTANDING OF BIOLOGICAL AND PHYSIOLOGICAL MECHANISMS THAT CONTROL REPRODUCTION IN CATTLE, SO THAT BETTER STRATEGIES TO IMPROVE GENETIC GAIN AND MAXIMIZE REPRODUCTIVE EFFICIENCY CAN BE DEVELOPED. THE EXPECTED OUTCOMES FROM THIS PROJECT ARE A CRITICAL STEP TOWARDS SUCH LONG-TERM GOAL AND IT IS LIKELY THAT, IN THE ABSENCE OF SUCH KNOWLEDGE, KEY INTERACTIONS AMONG GENETIC, PHYSIOLOGICAL, AND MANAGEMENT FACTORS WILL BE OVERLOOKED, LIMITING THE PROGRESS OF ANIMAL IMPROVEMENT PROGRAMS AND SUSTAINABILITY OF THE DAIRY INDUSTRY. · GrantIndex