# Presentation: 682119

## Domestic vs. imported AI semenfor Holstein graziers in the US

## Background

**Increasing interest in grazing to reduce costs (machinery, feed, labor)**
**Increased importance of fertility to synchronize calvings and pasture availability**
**New Zealand (NZ) has used grazing as the standard practice for many years**

## Assumptions

**US producers have used semen from some NZ bulls**
**Usage may be intended to capitalize on selection for grazing conditions**
**Value of NZ bulls might be for yield on pasture or better fertility**

## Objective

**To compare US performance of daughters of NZ Holstein-Friesian AI bulls with that of contemporaries with US Holstein AI sires**
**Traits**
**Milk, fat, and protein yields**
**Somatic cell score**
**Days open**
**Conformation**

## Data

**159 US herds with daughters of 26 NZ bulls and US-sired contemporaries**
**552 daughters of NZ bulls and 6,266 daughters of US bulls**
**Phenotypes for yield, SCS, and days open for parities 1, 2, and 3 and first conformation scores (79 NZ-sired vs. 308 US-sired cows)**

## Method

**In addition to studying all herds using NZ bulls, a “grazing” subset was defined by seasonal calvings**
**More than 3 times as many calvings for March—May as for September—November for 3 consecutive years during 2002—2005**
**11 herds had ********25 reported calvings/year**

## Results

|  | Parity 1 |  | Parity 2 |  | Parity 3 |  |
| --- | --- | --- | --- | --- | --- | --- |
| Milk (kg) | —481 | *** | —572 | *** | —479 | *** |
| Fat (kg) | 1 |  | 1 |  | 3 |  |
| Protein (kg) | —5 | ** | —7 | *** | —5 |  |
|  |  |  |  |  |  |  |
|  |  |  |  |  |  |  |

**Performance of NZ vs. US daughters****(NZ minus US)**

|  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- |
|  |  |  |  |  |  |  |
|  |  |  |  |  |  |  |
|  |  |  |  |  |  |  |
|  |  |  |  |  |  |  |
| Days open | —7 | .5* | —7 | .6* | —1 | .7 |

|  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- |
|  |  |  |  |  |  |  |
|  |  |  |  |  |  |  |
|  |  |  |  |  |  |  |
| SCS | 0 | .22*** | 0 | .10 | 0 | .06 |
|  |  |  |  |  |  |  |

## Results

| Significant differences |  |  |
| --- | --- | --- |
| Final score | —1 | .6* |
| Stature | —2 | .3* |
| Rear udder height | —2 | .6* |
| Udder depth | —3 | .2* |

**Conformation of NZ vs. US daughters****(NZ minus US)**

## Results

**But are these grazing herds? **
**Only 11 met seasonal calving requirement**
**Only 7% of herds, but 25% of NZ daughters**
**Although yield was lower for those 11 herds (8,647 vs. 9,418 kg milk), likely there was a grain-supplemented diet**

## Grazing Results

|  | Parity 1 |  | Parity 2 |  | Parity 3 |  |
| --- | --- | --- | --- | --- | --- | --- |
| Milk (kg) | —351 | *** | —538 | *** | —745 | *** |
| Fat (kg) | 3 |  | 2 |  | 6 |  |
| Protein (kg) | —4 |  | —8 | * | —13 | ** |
| SCS | 0 | .24* | 0 | .16 | 0 | .11 |
| Days open | —6 | .5 | —1 | .0 | —0 | .7 |

**Performance of NZ vs. US daughters****(NZ minus US)**

## Conclusions

**Some (much?) NZ semen likely used for reasons other than grazing characteristics**
**For all NZ daughters, milk and protein yields were lower, SCS higher, but days open less**
**For seasonal herds, NZ daughters again lower for milk yield, higher for SCS, higher for 3rd-lactation protein yield, and no longer significantly lower for days open**

## Conclusions

**To the degree that NZ semen was used to improve performance on pasture, only fertility was improved in first and second lactations**
**Daughters of NZ bulls were lower for final score and stature and had lower udders, perhaps because sire selection in NZ was at a much lower level of nutrition and production**