# Presentation: 693933

## Genetic Evaluation of Cow Fertility expressed as Pregnancy Rate

## Factors Affecting Fertility

**Service bull**
**Sperm motility, abnormality, etc. measured by AI companies**
**ERCR ratings from DRMS@Raleigh**
**Environment and genes of cow**
**Interaction of bull and cow**
**Lethal recessives, inbreeding**

## Pregnancy Rate

**Rate that cows become pregnant**
**Can be derived from days open**
**Non-linear: 21 / (DO – VWP + 11)**
**Linear approx: (233 – DO) / 4**
**Advantages over days open**
**Positive numbers are desirable**
**Earlier measure of herd fertility**

**Notes:**
VWP = Voluntary waiting period

## Distribution of Days OpenHolstein Calvings 1990 - 2001

**≤**** ****50**

**≥**** ****250**

**Distribution of Days Open****Holstein Calvings 1990 - 2001**

**Cows culled for reproductive reasons**

## Average breed effects across regions and time by calving month

## Regional effects for Holsteins calving since 1997

## Parameter Estimates Multi-trait REML analysis of first lactations

| Heritability of DO |  | 3.7% |  |
| --- | --- | --- | --- |
| Correlations with DO |  | Phenotypic | Genetic |
| Milk |  | .11 | .38 |
| Fat |  | .09 | .33 |
| Protein  |  | .10 | .32 |
| SCS |  | .05 | .30 |
| PL |  | -.20 | -.59 |

## Pregnancy Rate Evaluation

**Lactations 1-5 beginning with 1960**
**Data sources**
**Reported DO confirmed with next calving**
**Exclude most recent 9 months**
**Reported DO if no next calving**
**Exclude most recent 9 months**
**Calving interval – 280 days if no reported DO**
**Exclude most recent 18 months**
**Assigned DO = 250 if sold for infertility**

## Evaluation Methods

**BLUP Animal Model**
**Same programs used for yield, PL, SCS**
**Convert to preg rate = (233 – DO) / 4 **
**Adjust for heterogeneous variance**
**Parameter estimates used:**
**Heritability = ****4%**
**Repeatability = ****11%**
**Sire-by-herd interaction = ****1%**

## Evaluation Test Run

**Holstein**** data from Aug 2002 evaluation**
**40 million**** lactations**
**16 million**** cows**
**Statistics for recent, well-sampled bulls **
**Born 1994 - 1997**
**Milk REL > 80% (mean = 87%)**
**4215 ****Holstein**** bulls**
**314 ****Jersey**** bulls**
**Example evaluations for older sires**

## Recent Bull Evaluations

|  | Holstein | Jersey |
| --- | --- | --- |
| Pregnancy Rate |  |  |
| PTA range | -4.8 to +2.8 | -3.0 to +1.5 |
| REL mean  | 59% | 57% |
| PTA correlations |  |  |
| PL | .46 | .23 |
| SCS | -.13 | .03 |
| Milk  | -.22 | -.22 |
| Fat | -.18 | -.35 |
| Protein | -.16 | -.17 |

## Older Bull Evaluations

|  | REL | DO | DPR | PL | NM$ |
| --- | --- | --- | --- | --- | --- |
| Duster | 99 | -7 | +1.8 | +4.3 | +442 |
| Bellwood | 99 | +1 | -.3 | -.5 | +361 |
| Mandel | 99 | +9 | -2.3 | -.6 | +248 |
| Luke | 99 | +11 | -2.8 | -1.8 | +135 |
| Mountain | 99 | -3 | +.8 | +1.1 | +280 |
| Mascot | 99 | +5 | -1.3 | -2.9 | +29 |

**Notes:**
DO = Days Open
DPR = Daughter Pregnancy Rate

## Pregnancy Rate Genetic Trend 1957-1999

## Phenotypic Trend – Holstein DO

**5****th**

**4****th**

**3****rd**

**2****nd**

**1****st**

**Lactation**

## Conclusions

**Daughter Pregnancy Rate has low heritability (****~4%****) but high genetic correlation with Productive Life (****>.5****)**
**Official evaluations for DPR planned for February 2003**
**Selection on PL has greatly reduced the decline in cow fertility**
**Economic value not yet determined**

## Acknowledgments

**All DHIA herds and processing centers contributed data**
**George Wiggans and Lillian Bacheller improved the fertility database**
**John Clay suggested expressing cow fertility as pregnancy rate**