1. Measures of Fertility: Heritabilities and Genetic Correlations
Paul VanRaden, Duane Norman, and Bob Miller
Animal Improvement Programs Laboratory
ARS, USDA, Beltsville, MD

2. Analysis of Fertility Data
Individual breeding (ERCR) data from 2,195,643 Holstein and 145,976 Jersey lactations initiated 1998 – 2000
3447 Holstein sires and 3440 mating bulls
Cow and bull fertility evaluated separately
Multi-trait REML sire model

3. Cow Fertility Trait Heritabilities
Jersey
Holstein
Days to first breeding
4.0%
6.6%
Days to last breeding
2.9
4.0
Number of inseminations
2.2
1.8
70-d non-return rate to first service
1.1
1.0
Gestation length
10.3

4. Correlations with Days to Last Breeding
Traits (Holstein data)
Phenotypic
Genetic
Days to first breeding
.41
.85
Number of inseminations
.76
.61
70-d non-return rate to first service
-.32
-.21
Gestation length
-.02
-.01

5. Bull Fertility Analysis
Proportion of phenotypic variance was .5% for Holstein bulls, 1.2% for Jersey bulls
Correlation of REML solutions with ERCR
.71 for 446 bulls with > 300 services
.83 for 212 bulls with > 1000 services
.88 for 93 bulls with > 5000 services
Age of bull and country effects were removed, but could be included in solutions

6. Reporting of Cow Fertility
Reverse scale so positive is better?
Set mean = 100 like some Europeans?
Possible names and abbreviations
DO Days Open
DP Days Pregnant
CF Cow Fertility
DF Daughter Fertility
R Reproduction

7. Conclusions
Days to last breeding were most correlated genetically with days to first breeding (.85)
Non-return rate and number of services were less correlated because of lower heritabilities
Estimates similar to Weigel and Rekaya (2000)
Estimated variance for Holstein bull fertility agrees with value used in ERCR evaluation since May 2000