Genetic selection for reproduction
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Genetic selection for reproduction:. Current reproductive status of the national herd;. Application of selection indexes for dairy producers. 2007. Current reproductive status of the national herd. H.D. Norman. Dairy Cattle Reproductive Council Convention ( 2 ). Bull fertility.

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Genetic selection for reproduction

Genetic selection for reproduction:

Current reproductive status of the national herd;

Application of selection indexes for dairy producers


Current reproductive statusof the national herd

H.D. Norman

Dairy Cattle Reproductive Council Convention (2)

Bull fertility
Bull fertility

  • Estimated Relative Conception Rate (ERCR)

    • 70-day nonreturn rate (NRR)

    • Phenotypic evaluation

    • Source:

      • DRMS (Raleigh, NC), 1986−2005

      • USDA (Beltsville, MD), 2006−present

  • Western Bull Fertility Analysis

    • 75-d veterinary-confirmed conception rate

    • Source: AgriTech (Visalia, CA), 2003 −present

Survey of ai organizations
Survey of AI organizations

  • Does your organization rate bulls on fertility from field data?

  • Where do you obtain the data you use to evaluate them?

  • How long a time period is included in your evaluation?

  • What do you publish?

  • How many nonreturn days are in your calculation?

  • Is your evaluation derived from first or all services?

  • Do you eliminate cows sold before a specific number of days after insemination?

  • Do you eliminate cows in herds that go off test before a specific number of days after insemination?

  • Is information on services from natural service bulls that follow AI breedings available to you to document failures of those AI breedings?

Survey results
Survey results

  • All had programs to monitor bull fertility, but few relied completely on in-house information

    • Most received some information from technician breedings

    • One purchased breeding records from a dairy records processing center

    • Another obtained breeding records directly from cooperating herds

  • Most common fertility measure was NRR

    • Varied from 59 to 90 days for first breeding

    • Some organizations used a range of days

Survey results cont
Survey results (cont.)

  • Conception rate (CR) used by one because of availability of pregnancy-check records

  • Time period for data included in a bull’s fertility evaluation varied from 1 year to no limit

  • Equal number included only first services compared with all services

  • Data from technician breedings

    • Not adjusted for cow departures because of culling or when a herd discontinued production testing

    • No access to data that showed when natural service followed an AI mating

New usda service sire evaluation
New USDA service sire evaluation

  • Based on conception rate rather than NRR

  • More accurate

    • Inseminations from most of the United States

    • All services (not just first)

    • Additional model effects included

  • Available early 2008

  • Documentation at

Pregnancy rate pr
Pregnancy rate (PR)

  • Percentage of nonpregnant cows that become pregnant during each 21-day period

  • Advantages over days open (DO)

    • Easily defined

    • Information from nonpregnant cows included more easily

    • Larger (rather than smaller) values desirable

  • PR = [21/(DO − voluntary waiting period + 11)]100

    • Voluntary waiting period assumed to be 60 days

    • Factor of +11 adjusts to middle day of 21-day cycle

  • Examples

    • Herd with average of 133 DO has PR of 25%

    • Herd with average of 154 DO has PR of 20%

Usda pregnancy rate
USDA pregnancy rate

  • Linear approximation

  • PR = 0.25 (233 − DO)

  • 1% higher PR = 4 days fewer open

Daughter pregnancy rate dpr
Daughter pregnancy rate (DPR)

  • First USDA genetic evaluations in 2003

  • Same across-breed animal model as for yield traits, productive life (PL), and somatic cell score (SCS)

  • Heritability of 4%

  • Predicted transmitting abilities (PTAs) reported as percentages

    • Daughters of bull with PTA DPR of 1 expected to be 1% more likely to become pregnant during estrous cycle than if bull had PTA DPR of 0

    • Each increase of 1% in PTA DPR equivalent to decrease of 4 days in PTA DO

  • PTA DO approximated by −4 × PTA DPR

  • Example: Bull with PTA DPR of +2.0 would have PTA DO of −8






Application of selection indexesfor dairy producers

H.D. Norman

Dairy Cattle Reproductive Council Convention (31)

Dpr benefits over productive life
DPR benefits over productive life

  • Additional calves produced

  • Decreased units of semen needed per pregnancy

  • Decreased labor and supplies for heat detection, inseminations, and pregnancy checks

  • Higher yields because more ideal lactation lengths

Lifetime value
Lifetime value

  • Factors in determining economic value

    • Loss of about $1.50/DO

    • 2.8 lactations per cow

    • No breedings for half of cows during final lactation

    • Correlation of heifer and cow fertility (0.3)

    • Value of extra calves

    • Other unmeasured health expenses

  • Total lifetime merit value of $21/PTA DPR unit

Total performance index tpi
Total Performance Index (TPI)

  • Calculated by Holstein Association USA (Brattleboro, VT)

  • Emphasis of 19% on early breeding

    • 10% on PL

    • 8% on DPR

    • −1% on dairy form

  • 95% correlation between USDA lifetime net merit and Holstein TPI



H.D. Norman

Dairy Cattle Reproductive Council Convention (41)

Service sires
Service sires

  • Using bulls with higher conception rates returns profit fairly quickly

    • Premium of $2 could be paid for semen per 1% improvement in fertility

    • Unit of semen from bull with ERCR of +2 worth $8 more than unit from bull with ERCR of −2

  • Little genetic improvement in male fertility expected over time

  • Use bull fertility as a secondary selection trait after production and economic indexes

Selection for cow fertility
Selection for cow fertility

  • Selection for improved fertility possible and recommended

  • Most benefits delayed for 2 years or more

  • Select service sires for overall lifetime merit that includes daughter fertility rather than for daughter fertility alone

  • Producers with herd fertility problems may choose to emphasize DPR extensively, which can be done with little loss in overall net merit

Benefits of improved reproduction
Benefits of improved reproduction

  • Lower semen cost

  • Improved ability to optimize lactation and lifetime yields

  • Reduced culling due to delayed or failed conception

  • More herd replacements

Fertility emphasis
Fertility emphasis

  • Service-sire fertility and DPR important for all management systems, but most important for grazing herds with seasonal calving

  • Use of a few bulls that average 3.0% for PTA DPR (equivalent to a decrease of 12 DO) could recover much of genetic decline in fertility from use of high-yield bulls for 40 years

  • General recommendation still is to select for overall merit based on genetic-economic index appropriate for current milk market