# Presentation: 468892

## Accuracy of foreign dairy bull evaluations in predicting US evaluations for yield

## Previous Study

**Compared Interbull with National evaluations**
**Based predominantly on US bulls**
**Foreign data improves prediction**

**Notes:**
The previous study compared Interbull evaluations for accuracy in predicting future national evaluations.
Although we examined accuracies on five national scales, most bulls were from the US.
While it was clearly shown that foreign data improves prediction, little information on accuracy specifically addressed foreign bulls prediction of US PTA.

## Current Study

**Examined the predictive accuracy of foreign bull evaluations which did *****not***** include US daughters**

**Notes:**
The current Study examined the predictive accuracy of foreign evaluations, available through the Interbull service, which did not include US daughters.

## Data and Methods

**Holstein bulls**
**All data on US scale**
**Expressed on current US base**
**REL ******** 80% in February 2003 US evaluations**

**Notes:**
PTA from Feb. 2003 evaluations are the dependent variables.

## Data and Methods

**Independent variables:**
**Latest Interbull PTA including no US daughters (“latest foreign”)**
**1995 through 2002, February/August  **
**All and ******** 80% REL**
**Concurrent US Parent Averages (the alternative for sire selection)**

## Data and Methods

**Means for REL**
**Difference in Evaluations**
**SD of differences**
**Correlation related to expectation**

## Amount of Information

|  | All Bulls | Bulls with
 80% REL
In Latest Foreign Evaluation |
| --- | --- | --- |
| Number of Bulls | 272 | 237 |
| Mean REL |  |  |
| Latest Foreign PTA | 86% | 88% |
| Concurrent PA | 42% | 42% |
| Feb. 2003 US PTA | 91% | 92% |

**Notes:**
We had already required the bulls to have 80% REL for the US PTA, here we required the latest foreign REL to also be at least 80%.

## Differences All Bulls

|  | Latest Foreign Only PTA1 | Concurrent US PA2 |
| --- | --- | --- |
| Mean Differences |  |  |
| Milk (kg) | 10.3 | – 131.9 |
| Fat (kg) | – 0.1 | – 3.1 |
| Protein (kg) |  0.0 | – 3.6 |
| SD of Differences |  |  |
| Milk (kg) | 184.5 | 264.4 |
| Fat (kg) | 6.8 | 10.2 |
| Protein (kg) | 5.1 | 7.5 |
| 1 Foreign PTA minus US PTA (February 2003) |  |  |
| 2 US PA minus US PTA (February 2003) |  |  |

**Notes:**
On average, the latest foreign evaluation predicted the Feb PTA very well. The minus signs for PA mean that PA was an UNDER estimate of the later PTA. This is not our usual situation, but remember that the bulls we are looking at are the better bulls from elsewhere and we progeny tested there to identify those with positive Mendelian sampling.

SD of differences are sizeable, but these evaluations are from two separate groups of daughters, not the part-whole situation we are more accustomed to.

## Differences Bulls with REL 80% In Latest Foreign Evaluation

|  | Latest Foreign Only PTA1 | Concurrent US PA2 |
| --- | --- | --- |
| Mean Differences |  |  |
| Milk (kg) | 7.3 | –164.5 |
| Fat (kg) | – 0.2 | – 4.0 |
| Protein (kg) | – 0.1 | – 4.6 |
| SD of Differences |  |  |
| Milk (kg) | 163.5 | 249.0 |
| Fat (kg) | 6.2 | 9.8 |
| Protein (kg) | 4.6 | 7.0 |
| 1 Foreign PTA minus US PTA (February 2003) |  |  |
| 2 US PA minus US PTA (February 2003) |  |  |

**Notes:**
For the subset with at least 80% REL for the latest foreign evaluation, mean differences are even closer to zero for the foreign PTA and more negative for the US PA at the same time.

SD of differences are smaller as expected by the REL requirement.

## Correlations with 2/03 US PTAAll Bulls

|  | Latest Foreign Only PTA | Concurrent US PA |
| --- | --- | --- |
| Actual |  |  |
| Milk | .86 | .70 |
| Fat | .82 | .56 |
| Protein | .87 | .70 |
| Expected | .88 | .62 |

**Notes:**
For all 272 bulls, correlations between foreign only and US only PTA were high and very close to expectation, although fat is a bit lower. Correlation of US PTA with the earlier PA was higher than expected for mild and protein and lower for fat.

## Correlations with 2/03 US PTA Bulls with REL 80% In Latest Foreign Evaluation

|  | Latest Foreign Only PTA | Concurrent US PA |
| --- | --- | --- |
| Actual |  |  |
| Milk | .89 | .73 |
| Fat | .86 | .60 |
| Protein | .88 | .71 |
| Expected | .90 | .62 |

**Notes:**
We see the same picture for the subset where the actual correlations are all increased.

## Conclusions

**Interbull evaluations on average did not differ to an important degree from later US evaluations**
**Correlations generally near expectation**
**Interbull evaluations clearly superior to US PA available at same time**

**Interbull evaluations on average did not differ to an important degree from later US evaluations**
**Correlations generally near expectation**
**Interbull evaluations clearly superior to US PA available at same time**
**Interbull evaluations of foreign bulls are useful in predicting future US PTA **