Agriculture and Agri-Food Canada Agriculture et Agroalimentaire Canada 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

Agriculture and Agri-Food Canada Agriculture et Agroalimentaire Canada 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

Agriculture and Agri-Food Canada Agriculture et Agroalimentaire Canada Data 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?!?

Agriculture and Agri-Food Canada Agriculture et Agroalimentaire Canada Multiple Trait Selection Measure This Growth Cow weight Calves ÷ Reproductive years Evaluate This Maternal Productivity What is your MPI? Moo.

Agriculture and Agri-Food Canada Agriculture et Agroalimentaire Canada Trait 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

Agriculture and Agri-Food Canada Agriculture et Agroalimentaire Canada Multiple 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 = v 1 WWT + v 2 MLK + v 3 CWT + v 4 STY with resulting economic weights: v 1 = 1.17 v 2 = 0.98 v 3 = v 4 = 2.39

Agriculture and Agri-Food Canada Agriculture et Agroalimentaire Canada MPI NCE Genetic Parameters BWTd BWTm WWTd WWTm WWTpe CWTd STYd BWTd BWTm WWTd WWTm WWTpe CWTd STYd

Agriculture and Agri-Food Canada Agriculture et Agroalimentaire Canada Relative Emphasis The relative contribution of component traits to variation in the index –Weaning weight = 30% –Milk = 25% –Cow weight = 13% –Stayability = 27%

Agriculture and Agri-Food Canada Agriculture et Agroalimentaire Canada Making 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

Agriculture and Agri-Food Canada Agriculture et Agroalimentaire Canada MPI 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?

Agriculture and Agri-Food Canada Agriculture et Agroalimentaire Canada Component Traits in High and Low MPI Groups STY CWT MLK WWT

Agriculture and Agri-Food Canada Agriculture et Agroalimentaire Canada 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

Agriculture and Agri-Food Canada Agriculture et Agroalimentaire Canada … 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

Agriculture and Agri-Food Canada Agriculture et Agroalimentaire Canada Thank you