Impact of selection for increased daughter fertility on productive life and culling for reproduction

H. D. Norman, J. R. Wright*, R. H. MillerAnimal Improvement Programs Laboratory, Agricultural Research Service, USDA, Beltsville, MD 20705-2350

Abstract T19

INTRODUCTION

Improving reproductive traits through genetic selection was usually considered futile because of low heritability (<5%).

Pregnancy rate declined by 7% and days open increased by 39 days from 1960 To 2000.

AIPL began calculating genetic evaluations for daughter pregnancy rate (DPR) in 2003.

OBJECTIVE

Determine how effective emphasis on DPR for two generations was in changing fertility and productive life (PL).

CONCLUSIONS

Emphasis on DPR for 2 generations increased PL and decreased culling for reproduction.

Selection for PTA DPR can be effective in improving fertility.

DATA & METHODSData edits:

Holstein AI bulls with January 2008 PTA DPR based on 35 daughters.

Holstein cows with birth dates from 1988 through 1999 and calving dates from 1990 through 2005.

Cows excluded if they changed herds, had missing lactation records within first 5 parities, or were in herds with <10 cows.

Final data set of 4,380,300 cows in 31,759 herds.

Bulls assigned to 5 groups (quintiles) based on their PTA DPR.

Cows divided into 25 groups based on their sire and maternal grandsire (MGS) quintile for PTA DPR.

Examples: Cows in group 1,1 had both sires and MGS

in the lowest 20% of AI bulls for PTA DPR

Cows in group 5,5 had both sires and MGS in the highest 20% of AI bulls for PTA DPR

http://aipl.arsusda.gov/

RESULTS

Number of cows by ancestor PTA DPR group

2008

1,21,3

1,4

1,5

2,1

2,2

2,4

2,5

3,1

3,4

3,5

4,1

4,2

4,4

5,1

5,2

5,4

5,5

3,2

1,1

5,34,5

4,3

3,32,3

9.5

10

10.5

11

11.5

12

12.5

13

13.5

Percent cows reported culled for reproduction by ancestor PTA DPR group

1 2 3 4 51 238,63

2205,81

0191,13

5243,96

9286,41

82 182,66

3152,30

9144,73

2187,71

4224,41

13 150,57

4130,47

2127,80

4158,92

3204,80

94 162,17

7136,93

3132,42

6171,16

6218,87

35 133,63

6117,15

1114,30

8151,45

6211,79

9 Distribution of cows by group ranged from 2.6%

to 6.5%, most likely due to heavy use of certain bulls.

Sire and MGS PTA DPR mean by group (not shown) varied by over 4% (from -2.1 in group 1,1 to 2.1 in group 5,5).

PL was over 4 mo longer for cows with sires and MGS from the highest group than those from the lowest group.

Sire quintile had a larger effect on increasing length of PL (2.8 to 3.3 mo) than MGS quintile (0.8 to 1.4 mo).

Frequency of culling for reproductive reasons decreased over 3% from 13.1% (group 1,1) to 10.0% group (5,5).

Mean 1st parity pregnancy rate by ancestor PTA DPR group

First parity pregnancy rate rose from 20.0% for cows sired by the lowest PTA DPR ancestor group (1,1) to 27.3% for cows sired by highest (5,5).

1 2 3 4 51 -4.2 -3.8 -3.7 -3.3 -2.8 1.42 -3.0 -2.5 -2.5 -1.9 -1.5 1.43 -2.9 -2.5 -2.5 -2.2 -1.7 1.34 -2.1 -1.7 -1.6 -1.4 -0.9 1.25 -0.8 -0.6 -0.6 -0.3 0.0 0.8

3.3 3.2 3.1 3.0 2.8

MGS quintile

Sire quintile

1,2

1,3

1,5

2,12,2

2,4

2,5

3,1

3,23,3

3,5

4,1

4,2

4,5

5,15,25,3

5,5

1,1

5,4

4,44,33,4

2,31,4

18.0

20.0

22.0

24.0

26.0

28.0

Max. sire difference

Max. MGS differ-ence

Pre

gnancy

rate

(%

)

MGS quintile

Least-squares differences for percent culled for reproduction

1 2 3 4 51 1.9 1.7 1.5 1.2 1.1 0.82 1.6 1.3 1.2 1.0 0.9 0.73 1.2 1.1 0.8 0.7 0.5 0.74 0.6 0.5 0.3 0.1 0.2 0.45 0.4 0.3 0.2 0.0 0.0 0.4

1.5 1.4 1.3 1.2 1.1

MGS quintile

Sire quintile

Cows with low ancestor PTA DPR were culled for reproduction at a 2% higher rate than those with high ancestor PTA DPR.

Sire quintile and MGS quintile effect were nearly linear across groups.

Max. MGS differ-ence

Max. sire difference

4,1

4,44,3

3,5

3,1

2,2

2,42,5

1,1

3,4

1,4

1,2

5,25,1

5,55,4

5,3

4,5

4,2

3,33,2

1,5

2,3

2,1

1,3

24.0

25.0

26.0

27.0

28.0

29.0

DATA & METHODS (cont.)

Analysis: Examine least-squares differences between

cow groups on a within-herd basis with cow birth year in the model.

Sir

e q

uin

tile

RESULTS (cont.)

Mean of cow PL by ancestor PTA DPR group

RESULTS (cont.) Least-squares differences for PL (mo)

Overall productive life mean was 27.0 months.

Cows in the lowest PTA DPR ancestor group (1,1) had a mean PL of 25.0 while the highest group averaged 28.7 months.

The increase in PL was similar to the increase seen in first parity pregnancy rate.

First parity mature-equivalent milk mean was 1,230 kg lower in the highest PTA DPR group (5,5) than in the lowest (1,1).

PL

(mo)

% c

ulle

d