# Presentation: 662454

## Use of early lactation days open records for genetic evaluation of cow fertility  

**M.T. Kuhn* and P. M. VanRaden**
**USDA-AIPL, Beltsville, MD**

## Introduction

**- National genetic evaluation for female fertility introduced in February, 2003**
**- Evaluations are based on **_**Days Open (DO)**_
**- Current requirement:**
**Records must be a minimum of **_**250 days in milk**_

## Reason for 250 DIM Requirement

**- Avoid potential bias**
**- Sires poor for fertility:**
**	****	****- Only best daughters available early in **
**	****	****   ****lactation**
**	****	****	******** ****upward bias for poor sires**
**	**

## Consequence of 250 requirement:

**- Young bulls:**
**	****	****- First proof for *****yield***** 40 days after**
**	****	****  ****daughters initiate first lactation**
**	****	****- Must wait 7 more months for DPR **
**	****	****  ****evaluation**

## Objectives

**- Develop a predictor for DO**
**- Determine how early in lactation it can be used**

## Prediction Equation

**ŷ = ****	****Intercept   +**
**	****	****Lactation  +**
**	****	****Calving Ease (CE)    +**
**	****	****ß****1*****Age  +  ß****2*****Age****2****     +**
**	****	****ß****3*****Milk  +  ß****4*****Milk****2****  + **
**	****	****ß****5*****(DO based on last breeding)**

**- Models with**_***out***_** milk yield also examined**

## Prediction Equation

**- Model is fit separately for each of 9 DIM groups:**
**	****70,  90,  110,  130,  150,  170,  190,  210,  230**

_**Define:**_
**     ****DO70 = DO based on breedings up to 70 DIM**
**     ****DO90 = DO based on breedings up to 90 DIM**
**	****.****	****	****	****.**
**	****.****	****	****	****.**
**	****.****	****	****	****.**
**     ****DO230 = DO based on breedings up to 230 DIM**

## Evaluation of the Predictor

**- Bias:  Compare  ****ŷ  vs  y**
**- Cor(****ŷ, y)**
**	****	****- Phenotypic**
**	****	****- Genetic**
**- Compare:  PTA****ŷ****  and  PTA****y**

## DATA
- Breeding records from 4 DRPCs
- Years available: 1995-1999
- Date of breeding, service sire, service number 
   recorded for each service on each cow-lactation

**- ****Breeding records from 4 DRPCs**
**- Years available: 1995-1999**
**- Date of breeding, service sire, service number **
**   ****recorded for **_**each service**_** on each cow-lactation**

**2) Estimate genetic correlations**

**1) Estimate effects in prediction model, solutions to be used to calculate ****ŷ’s**

_**3 main things to do:**_

**3) Calculate PTAs:  PTA****y**** vs  PTA****ŷ**

## Estimation of Genetic Correlations

**- Vars/Covs estimated using REML**
**- Model for estimation:**
**	****	****y = HYSP  +  Sire  +  e**
**- 11 traits:**
**	****	****Actual DO, DO70, DO90, ..., DO230, Milk**
**- Data from 1995-1998**
**	****	**** ******** ********  ****670,000 records,  1000 sires**

## Comparing PTAs

**- Data from 1995-1998**
**	****	******** ****375,000 records**
**- Only 1998 records were predicted**
**	****	******** ****127,000 predicted records**
**- Animal model for calculation of PTAs:**
**	****	****y  =  HYSP  +  A  +  PE  +  e**

## RESULTSPercentage of cows with a breeding by DIM

**	****	****Days****	****	****Percent****	****Cumulative %**
**	****	****  ****70****	****	****    36****	****	****	****36**
**	****	****  ****90****	****	****    25****	****	****	****61**
**	****	**** ****110****	****	****    15****	****	****	****76**
**	****	**** ****130****	****	****      9****	****	****	****85**
**	****	**** ****150****	****	****      5****	****	****	****90**
**	****	**** ****170****	****	****      3****	****	****	****93**
**	****	****   ****.****	****	****       .****	****	****	****  .**
**	****	****   ****.****	****	****       .****	****	****	****  .**
**	****	****   ****.****	****	****       .****	****	****	****  .**
**	****    ****> 250****	****	****    1.4****	****	****         100**

## Phenotypic Comparisons

**Trait****	****	****Mean****	****	****Cor**
**Actual****	****138.8****	****	****   1****  **
**DO70****	****	****138.7****	****	**** .28**
**DO90****	****	****138.1****	****	**** .36**
**DO110****	****137.8****	****	**** .44**
**DO130****	****137.9****	****	**** .54**
**DO150****	****138.1****	****	**** .63**
**DO170****	****138.3****	****	**** .71**
**DO190****	****138.4****	****	**** .78**
**DO210****	****138.5****	****	**** .83**
**DO230****	****138.5****	****	**** .88**

## Genetic  Correlations of Predicted and Actual DO

**                ****	**** ****Prediction Model**
** ****Day****	****   W/ Milk****	****No Milk****	****Mix**_** **_
**   ****70****	****        .73****	****    .73****	****	**** .74**
**   ****90****	****        .80****	****    .80****	****	**** .80**
** ****110****	****        .85****	****    .86****	****	**** .86**
** ****130****	****       .90****	****   .91****	****	****.91**
** ****150****	****        .94****	****    .94****	****	**** .94**
** ****170****	****        .96****	****    .97****	****	**** .97**
** ****190****	****        .98****	****    .98****	****	**** .98**
** ****210****	****        .99****	****    .99****	****	**** .99**
** ****230****	****        .99****	****    .99****	****	**** .99**

## Genetic  Correlations of Predicted DO with Milk

**                ****	**** ****Prediction Model**
** ****Day****	****   ****W/ Milk****	****No Milk****	****Mix**_** **_
**   ****70****	****       .42****	****    .29****	****	**** .36**
**   ****90****	****       .44****	****    .33****	****	**** .36**
** ****110****	****       .45****	****    .35****	****	**** .36**
** ****130****	****       .45****	****    .36****	****	**** .36**
** ****150****	****       .42****	****    .35****	****	**** .35**
** ****170****	****       .39****	****    .34****	****	**** .34**
** ****190****	****       .38****	****    .33****	****	**** .33**
** ****210****	****       .35****	****    .32****	****	**** .32**
** ****230****	****       .34****	****    .31****	****	**** .31**

**Gen Cor of milk with Actual DO = .31**

## Cow PTAs Based on Actual vs Predicted Records

**	****	****	****	****	****    ****Mean*******
**	****	****	****DIM****	****	****PTA****ŷ****-PTA****y****	****	****Corr**
** ****	****	****	**** ****110****	****	****     -.06****	****	****  .90**
** ****	****	****	**** ****130****	****	****    -.007****	****	****  .92**
** ****	****	****	**** ****150****	****	****      .01****	****	****  .93**
**	****	****	**** ****110****	****	****     -.10****	****	****  .90**
**	****	****	**** ****130****	****	****     -.04****	****	****  .91**
**	****	****	**** ****150****	****	****     -.01****	****	****  .93**
**	****	****	*********Expressed in standard deviation units**

## Sire PTAs Based on Actual vs Predicted Records1

**	****	****	****    ****Mean****2****	****	****Corr****	****	****Rank**
**DIM****	****	****PTA****ŷ****-PTA****y****	****    (PTA****ŷ****, PTA****y****) ****	****Corr**
** ****110****	****	****    -.06****	****	****.93****	****	**** .92**
** ****130****	****	****   -.008****	****	****.94****	****	**** .93**
** ****150****	****	****     .02****	****	****	****.95****	****	**** .94**
**  ****1**** Predictor included milk if no breeding, no milk if with breeding**
**  ****2**** Expressed in standard deviation units**

## Conclusions

**1. Projection of DO records will utilize:**
**	****	****- Lactation**
**	****	****- Calving ease score**
**	****	****- Age**
**	****	****- DO based on last breeding**
**	****	****- Milk yield, if no breeding**
**2. Records can begin to be used at 130 DIM**
**	****	**** ******** ****Reduction of 4 months**