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1	Selection for Fertility in Dairy Cattle
2	Factors Affecting Fertility Environment and management Season, region, herd, age, milk yield Estrus detection and / or synchronization Voluntary waiting period Fertility of bull (ERCR in USA) Genes of cow (Dau. Pregnancy Rate) Interaction of bull’s and cow’s genes Inbreeding, recessives (CVM, DUMPS)
3	Fertility Does Not Show
4	For Fertility, You Need Data
5	Problem: Cows Are Less Fertile USA Holsteins 1965-2000
6	Coefficients of Variation (CV) Standard deviation divided by mean
7	Pregnancy Rate The percentage of nonpregnant cows that become pregnant during each 21-day time period Pregnancy rate < conception rate Cows that are not cycling Estrus not expressed or detected Typical pregnancy rates 20% if calving interval is 14.3 months 25% if calving interval is 13.6 months
8	Pregnancy Rate and Days Open
9	Sources of Fertility Data Percentages from 1998-1999 records
10	Distribution of Days Open Holstein Calvings 1990 - 2001
11	Seasonal Effects on Fertility Holsteins calving since 1997 in each USA region
12	USA Fertility Evaluation Holstein data in evaluation 44 million lactation records since 1960 17 million cows Lactations 1-5 are included Reliability for recently proven bulls 59% REL for Daughter Pregnancy Rate 61% REL for Productive Life 69% REL for Somatic Cell Score 85% REL for Milk Yield
13	USA Evaluation Methods Animal model, introduced Feb 2003 Same programs as yield, PL, SCS Compare cows within herd, season, and age Convert days open to pregnancy rate = (233 – DO) / 4 Parameter estimates used: Heritability = 4% Repeatability = 11% Sire-by-herd interaction = 4%
14	Recent USA Changes November 2003 and November 2004 Earlier evaluation of cow fertility Records in progress used at 130 instead of 250 days in milk Pregnancy exams used in prediction 6% gain in REL of DPR for new bulls Fertility used to predict longevity 4% gain in REL of PL for recent bulls
15	Selection for Longevity Productive Life introduced in USA in 1994 to select for longevity Genetic correlations with other traits: Daughter pregnancy rate = .59 Somatic cell score = -.35 Udder composite = .30 Daughter calving ease = -.24
16	Holstein Pregnancy Rate - Phenotypic and Genetic Trend 1965-2000
17	Value of Cow Fertility Fertility expenses per day open Heat detection ($20 / lact H .005) = $.10 Semen ($15 / unit + $5 labor) .025 = $.50 Pregnancy exam ($10 / exam).012 = $.12 Lactations too long or short = $.75 Value of DPR as % of total economic value 7% in Net Merit since August 2003 5% in TPI since February 2005, also -2% for dairy form in TPI since February 2005
18	Response to NM$ Selection Percent of single trait response
19	Heritability and Correlations Among Cow Fertility Traits
20	Cow Fertility Traits Evaluated in Largest Holstein Populations
21	Genetic Correlations of Traits Mark, 2003 EAAP meeting
22	Days Open Genetic Correlations Jorjani, 2005 Interbull Bulletin
23	Conception Rate Genetic Correlations Jorjani, 2005 Interbull Bulletin
24	Cow Fertility of Famous Bulls August 2005 USA data
25	Conclusions Fertility traits are less heritable but more variable than yield and type Selection for high yield reduces fertility Selection for longevity increases fertility Cow fertility traits receive 2% to 13% of total selection in many countries Bulls that sire good fertility are available