PhD Oral Defence: Genetic selection in Canadian dairy cattle

PhD Oral Defence of Bernard Ato Hagan, Animal Science

Most livestock producers and breeders seek to maximize genetic gains for economically important traits and at the same time increase the rate at which genetic gains are achieved. Genetic gains are only brought about by genetic selection. Dairy producers in Canada, however, do not have appropriate tools to monitor what selection and the amount of selection producers and AI organizations are making in their herds and studs, respectively. Genetic evaluations for Canadian Holstein, Ayrshire, Jersey, and Brown Swiss dairy cattle breeds were used to define and compute the realized genetic selection differentials (GSD) for 28 economically important traits and to investigate generation intervals in the four dairy cattle populations along the 4-path selection model. The findings from this study indicate that year of conception was the main environmental factor that was most important in the GSD realized in all four paths of selection (male-to-male, female-to-male, male-to-female, and female-to-female), whilst there were considerable variations in the GSD realized among herds in all four dairy cattle populations.

The results from the analyses in this study have been used to develop a prototype software tool and visualization model to help dairy producers and advisors monitor the selection realized in their individual dairy herds. This will enable dairy producers to determine whether the selection they are making align with their breeding objectives. The concept of the developed software tool is applicable to all livestock species for which genetic evaluations are routinely computed and published.

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