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This report provides insights into cow fertility trends, including Holstein regional averages, the genetic merit of high-DPR Holstein bulls, and the benefits of improved reproduction. It also explores reproductive evaluations, such as fertility of bulls and daughters, and offers recommendations to breeders.
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AIPL Report: We’re from the government and we’re here to help you!
1 2 3 4 5 Trend in days open Lactation
Benefits of improved reproduction • Lowers your semen cost • Optimizes cows lifetime yields • Reduced culling due to delayed or failed conception, i.e. less need for herd replacements • Provides more herd replacements
Two tall tales • Reproduction is only a management issue • Genetics cannot help solve fertility problems
Reproductive evaluations • Fertility of bull as a service sire • Fertility of bulls’ daughters when they reach breeding age
Bull fertility evaluations • Estimated Relative Conception Rate (ERCR) • 70-day nonreturn rate (NRR) 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
New service sire evaluation coming • 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 in late Spring/Summer 2008
Pregnancy rate (PR) • Percentage of open cows between 50 and 250 days in milk that become pregnant during each 21-day period • Advantages over days open (DO), the days from calving to conception • Easily defined • Information from nonpregnant cows included • Larger values preferable
Pregnancy rate (PR) • 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 70 DO has PR of 100% • Herd with average of 91 DO has PR of 50% • Herd with average of 133 DO has PR of 25% • Herd with average of 154 DO has PR of 20%
USDA pregnancy rate • Linear approximation • PR = 0.25 (233 − DO) • 1% higher PR = 4 days fewer open
Reproductive evaluations • Fertility of bulls’ daughters when they reach breeding age
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%
DPR (continued) • 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 equals a 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
Lifetime value • Factors in determining economic value to DPR • 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
What if I follow the Recommendations… • Question: What happens if folks selects for one of those fitness traits we provide? • Issue: Before 1994 there was an academic discussion on what happens if we lower the SCS too much, and then cows have to face a mastitis challenge? • We proceeded providing PTA SCS and built it into Net Merit so theoretically there is potential for this issue to still be questioned!
Research the potential problem • Using field data less costly; using research herds would be expensive • Group all AI Holstein bulls with 35 or more daughters into 5 equal groups based on PTA SCS • Look at data across 2 generations (sire and maternal grandsire (MGS))
Mean daughter 1st lactation age-adjusted SCS by sire-mgs PTA SCS group
Percent of cows culled for mastitis by sire-mgs PTA SCS group
Percent of cows culled for reproductive reasons by sire-mgs PTA DPR group
2008 Conclusions H.D. Norman NDHIA San Antonio (45)
Recommendations to breeders • Usual recommendation: Don’t select bulls solely on one trait because many traits have economic value • Consider economic value of all performance traits in your own market when making genetic choices • Dairies with seasonal calving should find an index that puts more weight on daughter fertility than those recommended for the general industry
Selection for bull fertility • Breeding to bulls with higher conception rates returns a profit fairly quickly • Premium of $2 could be paid for semen per 1% improvement in fertility • Thus, a unit of semen from bull with ERCR of +2 is worth $8 more than a unit from bull with ERCR of −2 • Use bull fertility as a secondary selection trait after picking bulls on their economic indexes
Selection for cow fertility • Selection for improved fertility will pay off, even though the benefit is delayed for 3 years • Choose your sires based on lifetime economic merit that includes daughter fertility, rather than for daughter fertility alone • However, producers with herd fertility problems could emphasize DPR extensively with little loss in overall net merit
Fertility emphasis • Service-sire fertility and DPR especially 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 neutralize much of genetic decline in fertility from use of high-yield bulls for 40 years • Select for overall merit based on genetic-economic index appropriate for your situation
