Selection indices in retrospect for dairy cattle

• Main Author: Brown, Timothy P. (Timothy Phillip)
• Format: Others
• Language: en
• Published: McGill University 1989
• Subjects: Dairy cattle > Breeding > Selection indexes.
• Online Access: http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59266

Selection differentials and selection indices in retrospect were calculated to determine the relative emphasis placed on production and type traits through bull selection. Indices in retrospect including only production traits indicated that, for Holsteins, fat yield was the trait most heavily selected for between 1978 and 1987, followed by protein percent and then milk yield. Fat percent and protein yield had negative index weights throughout the nine year period. In Ayrshires, similar weights were observed except that milk yield index weights were negative throughout the nine year period. It was found that the relative weight placed on type was small and did not affect the relative weights place on production traits. Within Holsteins, differences in bull selection when multiple services were required to successfully service a cow indicated that selection for overall size was reduced in later services. Within Ayrshires, there were no differences in any production or type trait within multiple services.