Agriculture and Agri-Food Canada Agriculture et Agroalimentaire Canada Multiple Trait Selection for...

Agriculture andAgri-Food Canada

Agriculture etAgroalimentaire Canada

Multiple Trait Selection for Maternal Productivity

Multiple Trait Selection for Maternal Productivity

D. H. Crews, Jr., P. B. Mwansa and R. A. Kemp

Agriculture and Agri-Food Canada Research Centre, Lethbridge, AB



What is maternal productivity?What is maternal productivity?

• Reproductive rate– Age at puberty– Heifer pregnancy rate, calving ease and 3 yr old rebreed rate– Persistence into profitable parities

• Calf growth– Direct genetics for growth– Maternal genetics milk production

• Cow maintenance requirements– Weight– Intake Can’t measure this

Low heritability, Difficult evaluation

Everyone already does this



Data and InformationData and Information

• One obstacle to new index development is capturing information on “new” traits

• We are often limited by what data is routinely and comfortably recorded in national databases

You want to

measure what?!?



Multiple Trait SelectionMultiple Trait Selection

Measure This

• Growth• Cow weight• Calves ÷ Reproductive years

Evaluate This

• Maternal Productivity

What is your MPI?

Moo.



Trait DefinitionsTrait Definitions

• Direct weaning weight• Maternal weaning weight• Cow weight at calf weaning

– Indicator for maintenance costs

• Stayability– Pr(3 | 1) = probability that a female will have at

least three calves given she became a dam



Multiple Trait Selection Index: ObjectiveMultiple Trait Selection Index: Objective

• The selection objective was to increase genetic potential to consistently wean heavy calves while maintaining input costs which yielded an aggregate genetic value function:

MPI = v1 WWT + v2 MLK + v3 CWT + v4 STY

with resulting economic weights:v1 = 1.17

v2 = 0.98

v3 = -0.14

v4 = 2.39



MPI NCE Genetic ParametersMPI NCE Genetic Parameters

0.74

-0.34

0.67

-0.45

-0.24

0.85

-0.44

-0.17

0.01 -0.48

0.48

0.11

0.19

0.18

0.24

0.50

0.07

BWTd

BWTm

WWTd

WWTm

WWTpe

CWTd

STYd

BWTd BWTm WWTd WWTm WWTpe CWTd STYd



Relative EmphasisRelative Emphasis

• The relative contribution of component traits to variation in the index– Weaning weight = 30%– Milk = 25%– Cow weight = 13%– Stayability = 27%

WWT

MLK

CWT

STY



Making the MPI User FriendlyMaking the MPI User Friendly

• The MPI can be interpreted as any other EPD– It is a combination of EPD with relative economic

values– The units are $ differences

• Information packaging is an important part of making indexes useful selection tools rather than only marketing tools

• The MPI can be expressed with any mean and variance– e.g. mean = 100, SD = 25



MPI ValidationMPI Validation

• What differences in animals are we evaluating?– Is the MPI the same as selection for component traits?

• Separation of MPI evaluation into high and low groups– High = > 2 SD greater than the mean MPI (n = 17,328)– Low = > 2 SD less than the mean MPI (n = 11,496)– Comparison of standardized component EPD between

groups

• What component traits are most related to the MPI?



Component Traits in High and Low MPI GroupsComponent Traits in High and Low MPI Groups

STY

CWT

MLK

WWT

-10 -5 0 5 10



To Summarize…To Summarize…

• The MPI was developed with the breeding objective to increase genetic potential to consistently wean heavier calves over a sustained productive life while maintaining input costs

• Annual or generational genetic trend is expected to be positive for all component traits, however, cow weight increases would be minimal

• As a multiple trait index, component trait values vary:– Animals with different component EPD have similar MPI



… Summary… Summary

• The MPI places more relative emphasis on maternal characteristics and stayability than on growth

• Accuracy and intensity are greatly reduced when data (information) is lacking on grandprogeny

• MPI selection is not equivalent to selection for any of the component traits alone

• Validation with maternal indexes is a challenge– MPI validation is still largely to be conducted

• The MPI needs to be expanded to include more components, which will come with data



Thank you

[email protected]

Agriculture and Agri-Food Canada Agriculture et Agroalimentaire Canada Multiple Trait Selection for...

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