Potential Consequences Of Selection On Gestation Length On Holstein Performance

1
Potential Consequences Of Selection On Gestation
Length On Holstein Performance
2
Introduction

• Genetic evaluations for gestation length (GL)
  were recently calculated (Norman et. al., 2009)
• Although GL can be changed genetically, the
  preferred direction is not clear
• Selection for GL could have indirect economic
  effects through correlations with cow or calf
  health and longevity

3
Objectives

• Determine if genetic evaluations of GL were
  accurate and repeatable
• To assess the consequences of changing GL on
  subsequent milk and fitness traits

4
Data and methods

• Predictor data
• PTA GL derived from calvings between Jan. 1998
  and Dec. 2005
• Stratify 1,620 Holstein bulls with at least 300
  breedings into 7 groups (-3.01, -3.00 to -2.01,
  1.00 to 1.99, and 2.00) according to PTA GL
• Predictee data
• Phenotypic data of 261,598 Holstein first parity
  cows calving 2006 - 2009 mated to same bulls

5
Model to examine effectiveness of PTA GL

• Phenotypic trait
• Herd-yr of conception
• Service sire PTA GL group
• Cow conception day
• Cow conception day squared
• Error

6
Traits predicted

• GL (d)
• Milk (kg)
• Fat (kg)
• Protein (kg)
• SCS

• Calving Ease score
• Stillbirth ()
• Days Open
• Culled ()
• Productive Life (mo)

7
What / when traits were measured
Productive Life
Culled
Gestation length
Days open
Cows 1st calving
Cows 2nd calving
Cows 3rd calving
CE, SB
Milk, fat, protein, SCS
8
Least squares means for gestation length
SS PTA GL group Mate GL
-3.01 275.3
-3.00 to -2.01 276.5
-2.00 to -1.01 277.8
-1.00 to -0.01 278.6
0.00 to 0.99 279.5
1.00 to 1.99 280.6
2.00 281.7
9
Least squares means of prediction of mate GL from
service sire PTA GL
b 1.01 0.02
10
Least squares means for production traits
SS PTA GL group Milk Fat Protein SCS
(kg) (kg) (kg) ()
-3.01 11,611 426 350 2.70
-3.00 to -2.01 11,616 425 351 2.69
-2.00 to -1.01 11,681 427 352 2.69
-1.00 to -0.01 11,710 428 353 2.68
0.00 to 0.99 11,724 429 353 2.68
1.00 to 1.99 11,745 429 353 2.69
2.00 11,695 427 352 2.70
11
Least squares means of prediction of 2nd parity
ME Protein from service sire GL group
12
Least squares means for fitness traits
SS PTA GL group Days open Calving ease Still-born Culled PL
(d) (1-5) () () (mo)
-3.01 142.8 1.30 3.3 19.1 34.8
-3.00 to -2.01 142.2 1.32 4.3 19.4 34.9
-2.00 to -1.01 140.4 1.34 4.2 19.4 34.8
-1.00 to -0.01 142.5 1.36 4.5 19.2 34.9
0.00 to 0.99 141.2 1.36 4.7 19.5 34.8
1.00 to 1.99 143.5 1.38 4.4 20.4 34.5
2.00 144.7 1.42 5.7 20.4 34.5
13
Least squares means of prediction of 2nd parity
stillbirth () from service sire GL group
14
Least squares means of prediction of 2nd parity
days open from service sire GL group
15
Least squares means of prediction of Productive
life from service sire GL group
16
Model to examine GL effect on subsequent
lactation (phenotypic)

• Phenotypic trait
• Herd-yr of conception
• Cow 1st parity gestation length group
• Cow conception day
• Cow conception day squared
• Error

17
Least squares means for 2nd parity production
traits
Cow 1st parity GL group Milk Fat Protein SCS
(kg) (kg) (kg) ()
271 11,094 407 339 2.69
272-273 11,445 419 347 2.70
274-275 11,560 422 350 2.69
276-277 11,661 426 352 2.69
278-279 11,751 429 354 2.68
280-281 11,806 431 355 2.70
282-283 11,858 433 356 2.69
284-285 11,895 435 357 2.67
286 11,941 436 357 2.68
18
Least squares means of 2nd parity ME Protein (kg)
by cow 1st parity GL group
19
Least squares means for 2nd parity fitness traits
Cow 1st parity GL group Days open Calving ease Stillborn Culled PL
(d) (1-5) () () (mo)
271 142.8 1.41 12.5 23.0 33.6
272-273 141.8 1.33 6.1 19.8 34.4
274-275 140.1 1.32 4.5 18.6 34.7
276-277 140.8 1.32 3.8 18.4 34.8
278-279 141.2 1.32 3.3 18.0 34.9
280-281 141.6 1.34 3.0 18.1 34.8
282-283 142.2 1.37 3.3 17.8 34.8
284-285 142.3 1.39 3.4 18.1 34.6
286 146.3 1.48 4.4 19.1 34.2
20
Least squares means of 2nd parity stillbirth ()
by cow 1st parity GL group
Twins removed
21
Least squares means of 2nd parity days open by
cow 1st parity GL group
22
Least squares means of Productive life by cow 1st
parity GL group
23
Model to examine relationship of dams GL on
daughter lactation

• Daughter phenotypic trait
• Herd-yr dam conceptionyr of daughter conception
• Dam gestation length group
• Dam age at conception (linear)
• Cow conception day
• Cow conception day squared
• Error

24
Daughters traits predicted
Productive Life
Culled
Gestation length
Days open
Cows 1st calving
Cows 2nd calving
Milk, fat, protein, SCS
CE, SB
25
Least squares means for daughter 1st parity GL
Dam GL group Dau GL (d)
271 277.3
272-273 277.4
274-275 277.8
276-277 278.2
278-279 278.7
280-281 279.3
282-283 279.8
284-285 280.3
286 280.8
26
Least squares means for daughter 1st parity
production traits
Dam GL group Milk Fat Protein SCS
(kg) (kg) (kg) ()
271 11,752 426 350 2.77
272-273 11,788 428 351 2.77
274-275 11,788 428 351 2.75
276-277 11,791 428 351 2.75
278-279 11,786 428 351 2.74
280-281 11,761 428 350 2.73
282-283 11,750 428 350 2.72
284-285 11,731 428 349 2.72
286 11,687 427 348 2.71
27
Least squares means for daughter fitness traits
Dam GL group Days open Calving ease Stillborn Culled PL
(d) (1-5) () () (mo)
271 133.0 1.40 5.1 10.1 33.6
272-273 135.1 1.40 4.9 10.0 33.8
274-275 137.2 1.40 5.2 9.8 33.8
276-277 139.0 1.41 5.2 9.9 33.8
278-279 140.3 1.42 5.1 10.1 33.8
280-281 141.9 1.42 5.1 10.2 33.7
282-283 143.5 1.44 5.2 10.1 33.6
284-285 144.0 1.44 5.7 10.4 33.5
286 144.6 1.45 5.6 10.4 33.3
28
Conclusions

• Gestation length can be changed through choice of
  service sire
• Relationship between GL and subsequent
  performance was small
• Little evidence found that shortening or
  increasing GL would provide an advantage overall
• Little influence from dams GL evident across
  generations