# Presentation: 422160

## Effect of herd by sire interaction variance on genetic evaluations

## Introduction

**For almost 40 years, U.S. genetic evaluations have accounted for genotype-environment interaction.**
**The animal model includes a term for interaction effects of sire and herd****.**
**Multiple daughters of a bull in the same herd have reduced weight.**

## History of Herd x Sire Effect

**Magnitude of H x S variance  (c****2****) estimated to be 14% in 1968 ****(Plowman and McDaniel JDS 51:306)**
**More recent research estimated c****2**** to be as low as 2% ****(Dimov et al, 1995 JDS 78:939)**** **
**As a result, c****2****  lowered to 10% in 1997. **

## Methods – November 2004

**Official November 2004 predicted transmitting abilities (PTA) for Holstein protein yield with c****2**** = 10% were compared with PTA computed with reduced c****2 ****of 5% and 1%.**
**Repeatability of protein yield was held constant at 0.55 by increasing permanent environmental variance (p****2****) as c****2**** was decreased.**

## Herd × Sire Variance: Maximum Daughters / Herd

| Trait | h2 | c2 | p2 | Maximum |
| --- | --- | --- | --- | --- |
| Yield | 30 | 1 | 24 | 85.0 |
|  | 30 |   5 | 20 | 17.0 |
|  | 30 |   7 | 18 | 12.1 |
|  | 30 | 10 | 15 |   8.5 |
| Yield | 35 |   8 | 12 | 10.3 |
| PL | 8 |   5 |   0 | 19.2 |
| SCS | 12 |   5 | 18 | 18.8 |

## Herd x Sire Variance:       Daughters / Herd 

**1% H****×****S**

**  ****5% H****×****S**

**10% H****×****S**

## Mean PTA protein (kg)

| c2 | Bulls | Cows |
| --- | --- | --- |
| 10% | 18.4 | 8.2 |
| 5% | 18.3 | 8.1 |
| 1% | 18.2 | 8.0 |

## Mean reliability protein (%)

| c2 | Bulls | Cows |
| --- | --- | --- |
| 10% | 88.6 | 49.3 |
| 5% | 89.2 | 49.4 |
| 1% | 90.0 | 49.4 |

## Correlation with official PTA(c2 = 10%)

|  c2 | Bulls | Cows |
| --- | --- | --- |
| 5% | 0.999 | 0.999 |
| 1% | 0.993 | 0.994 |

## Summary:top 100 active AI bulls

**With c****2**** reduced from 10 to 5%**
**98 bulls had no change in PTA protein**
**2 bulls had PTA changes of 1 kg**
**With c****2**** reduced from 10 to 1%**
**92 bulls had no change in PTA protein **
**8 bulls had changes of 1 or 2 kg**

## Summary:cows born since 1997

**Of 2.3 million recent cows, PTA protein changed >4 kg for:**
**20 cows when c****2**** = 5% **
**1256 cows when c****2**** = 1%**
**Cows changing the most were sired by non-AI bulls with many daughters in one or a few herds.**

## Implementation – May 2005

**H x S variance for yield traits was reduced from 10% to 7% of total.**
**Repeatability for yield traits was held constant at 55% by increasing permanent environmental variance (p****2****) from 15% to 18% of total.**
**For DPR, c****2**** was 1%, now is 4%.**

## May 2005 Herd × Sire Variances: Maximum Daughters / Herd

| Trait | h2 | c2 | p2 | Maximum |
| --- | --- | --- | --- | --- |
| Yield | 30 |   7 | 18 | 12 |
| Yield (J, B) | 35 |   7 | 13 | 12 |
| PL | 8 |   5 |   0 | 19 |
| SCS | 12 |   5 | 18 | 19 |
| DPR | 4 | 4 | 5 | 25 |

## Herd × Sire Variance:Daughters / Herd 

**5% H****×****S**

**  ****7% H****×****S**

**10% H****×****S**

## Changes from reducing c2 from 10% to 7%

**99 of the top 100 active AI bulls changed less than 1 kg PTA protein, only 1 bull changed 1 kg. **
**597 cows changed >4 kg protein out of 2.3 million recent cows. **
**.999 correlation for both bulls and cows.**

## Foreign experience

**Great Britain had herd-by-sire interaction in lactation model but not in test day model research.**
**Several single herd bulls rose towards the top, so a H x S effect was added back into the new test day model in May.**

## Conclusions

**Reduction of c****2**** from 10% to 7% will facilitate AI companies obtaining more daughters per herd in large cooperating herds. **
**The H x S interaction protects against chance or fraud when sampling is limited to few herds.**

## Further study ideas

**Use of a relationship matrix among herd by sire or herd by animal interactions could be helpful but was not tested in the current studies.**
**Interactions of sire or animal with region, climate, or country could be useful in the future.**