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Agriculture and Agriculture et Agri-Food Canada 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 Agriculture et Agri-Food Canada Agroalimentaire Canada What is maternal productivity? • Reproductive rate – Age at puberty – Low Heifer pregnancy rate, calving ease and 3 yr old rebreed rate heritability, Difficult evaluation – Persistence into profitable parities • Calf growth – Direct genetics for growth Everyone already – Maternal genetics milk production • does this Cow maintenance requirements – Weight – Intake Can’t measure this

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

Agriculture and Agriculture et Agri-Food Canada 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 Agriculture et Agri-Food Canada 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 = -0. 14 v 4 = 2. 39

Agriculture and Agriculture et Agri-Food Canada Agroalimentaire Canada MPI NCE Genetic Parameters BWTd BWTm WWTd WWTm WWTpe CWTd STYd 0. 48 BWTm 0. 11 WWTd 0. 74 0. 19 WWTm -0. 34 -0. 24 0. 18 0. 24 WWTpe CWTd 0. 67 0. 85 -0. 17 0. 50 STYd -0. 45 -0. 44 0. 01 -0. 48 0. 07

Agriculture and Agriculture et Agri-Food Canada 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 Agriculture et Agri-Food Canada 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 Agriculture et Agri-Food Canada 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 Agriculture et Agri-Food Canada Agroalimentaire Canada Component Traits in High and Low MPI Groups STY CWT MLK WWT -10 -5 0 5 10

Agriculture and Agriculture et Agri-Food Canada 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 Agriculture et Agri-Food Canada 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 Agriculture et Agri-Food Canada Agroalimentaire Canada Thank you [email protected] gc. ca 403 -317 -2288