Introduction
Genetic selection goals for dairy cattle, originally
aimed at production traits only, have been expanded
in stages over the past 30 years in most countries to
include more target traits covering production, functionality
and health and fertility. Each addition to
the selection goal often involves the use of additional
measured phenotypic traits (Cunningham &
Tauebert 2009) and requires knowledge of the correlations
between the new traits and those already in
the breeding goal. In the UK and the US Holstein
dairy industries, typical selection criteria traits
include milk, fat and protein yield, productive lifespan,
somatic cell count (SCC), udder composite