# Presentation: 469961

## Effect of Synchronization Protocols on Days Open and Pregnancy Rate at 120 Days in Dairy Cattle 

## Reproductive Performance

- History
- Decreasing performance over time
- Negative correlation with production traits
- Poor performance costly to producers
- Use of synchronization protocol
- Numerous protocols available
- Dependent upon herd
- Variety of herd applications

**Notes:**
Increased cost for pregnancy
Lower frequency on farm replacements
Longer calving interval
 decreased milk production

## Objectives

- Determine effects of synchronization protocols on genetic parameter estimates for:
- Days open (DO)
- Pregnancy rate at 120 days (PR120)
- Evaluate best approach to analyze reproduction field data with synchronization

**Notes:**
Focus on DFB and DO for AIPL seminar

## Traits

- Days open (DO)
- Includes interval from calving to first breeding (DFB) and the interval from breeding to conception
- Current selection on related trait (DPR)
- Handles cows that do not breed back
- Pregnancy rate at 120 d (PR120)
- Categorical trait
- Reflects 13 month calving interval
- Available before DO, less censoring

**Notes:**
- No information on cows that don’t conceive or aren’t given the chance to conceive
Can either remove these observations, are assign arbitrarily large values for DO
Either approach biases the results

## Data Collection

- 64 herds on progeny testing program
- Utilized Dairy Comp 305 herd software
- 50% sire identification and 75% breeding information
- Data requirements:
- Recorded fresh event
- First complete lactation (max. 6th)
- DFB between 37 d and 300 d
- DO between 37 d and 500 d
- Calving year between 1999 and 2002

## Models

- Sire models for both traits
- Base Model
- Fixed effects: lactation, age at freshening (months), herd-year-season
- Random effects: sire and residual
- Expanded Model
- Base model plus fixed effect for synchronization
- Interaction Model
- Expanded model plus random effect for sire-by-herd management interaction

**Notes:**
Will need modification if omitting PR120

## Data Analysis

- 2 classifications investigated
- Complete data set with various models
- Herd Management Category
- Estimation Methods
- DO: Gibbsf90 to create posterior distribution
- Median and SD among iterations
- PR120: Probit.f90 threshold program
- Mean and SD among iterations

**Notes:**
Previous investigation into the use of event codes suggested breeding codes for each breeding event were more useful at determining synchronization

## Herd Management Categories

- Herds classified by:
- Level of synchronization use
- Herd DFB standard deviation
- Three categories:
- STH- standing heat herds
- Average 19% synch, 30.1 DFB SD
- TAI- timed breeding herds
- Average 81% synch, 13.7 DFB SD
- MIXED- mixed management herds

**Notes:**
Synchronization was based on bred codes as before

## TAI Herd: 1st Breedings

**Notes:**
Layout of graph
	x-axis: days from beginning of data set
	y-axis: days in milk
	symbols: solid 1st breeding, open 2nd breeding/ circle non-synch triangle synch + is uuencoded
Very narrow band of breedings
Large frequency of synchronization

## TAI Herd: 1st & 2nd  Breedings

**Notes:**
Layout of graph
	x-axis: days from beginning of data set
	y-axis: days in milk
	symbols: solid 1st breeding, open 2nd breeding/ circle non-synch triangle synch + is uuencoded
Very narrow band of breedings
Large frequency of synchronization

## STH Herd: 1st Breedings

**Notes:**
Layout of graph
	x-axis: days from beginning of data set
	y-axis: days in milk
	symbols: solid 1st breeding, open 2nd breeding/ circle non-synch triangle synch + is uuencoded
Very narrow band of breedings
Large frequency of synchronization

## STH Herd: 1st & 2nd  Breedings

**Notes:**
Layout of graph
	x-axis: days from beginning of data set
	y-axis: days in milk
	symbols: solid 1st breeding, open 2nd breeding/ circle non-synch triangle synch + is uuencoded
Very narrow band of breedings
Large frequency of synchronization

## Mixed Herd: 1st Breedings

**Notes:**
Layout of graph
	x-axis: days from beginning of data set
	y-axis: days in milk
	symbols: solid 1st breeding, open 2nd breeding/ circle non-synch triangle synch + is uuencoded
Very narrow band of breedings
Large frequency of synchronization

## Mixed Herd: 1st & 2nd  Breedings

**Notes:**
Layout of graph
	x-axis: days from beginning of data set
	y-axis: days in milk
	symbols: solid 1st breeding, open 2nd breeding/ circle non-synch triangle synch + is uuencoded
Very narrow band of breedings
Large frequency of synchronization

## Herd Management Category:Median DO and Mean PR120

**Notes:**
Synchronization did not reduce the mean DFB or DO
First synch larger for DFB, suggests selective use
Later synchronization larger DO, suggests use of synch on problem animals

## Variance & Heritability: DO

|  Model | σ2s | σ2r | h2 |
| --- | --- | --- | --- |
| Base | 80.7 | 7446 | 0.04 |
| Expanded | 54.2 | 6638 | 0.04 |
| Interaction* | 46.4 | 6633 | 0.03 |
| *Variance for sire-by-herd management interaction was 12.6. |  |  |  |

## Variance & Heritability: PR120

|  Model | σ2s | h2 |
| --- | --- | --- |
| Base | 0.029 | 0.11 |
| Expanded | 0.028 | 0.11 |
| Interaction* | 0.025 | 0.10 |
| *Variance for sire-by-herd management interaction was 0.021.
 |  |  |

## Variance & Heritability: Data Subsets

- Herd Management Category
- Lower variance estimates for timed breeding herds
- Larger sire and animal variance and h2 for standing heat herds
- Variances for mixed herds were intermediate

## Conclusions

- Effect of synchronization on parameters
- Reduced residual variance
- Slight reduction in sire and residual variances
- Negligible effect on heritability
- Account for differences in protocol
- Detection of estrus vs. timed breeding
- Account for each protocol individually
- Herd application of protocols
- (Uniform vs. select)

**Notes:**
Reduced residual variance did not greatly reduce the heritability
Immediate lump data set together alright
Sire interactions accounted for by fixed effect
Greater difference among data sets
Lesser extent among base and expanded models
Reduced sire variance suggests genetic differences between sires
Fixed effect pulls it out
May be due to response or need for synch (problem)