A retrospective analysis of culling in a large AI stud

Abstract

SUMMARYOf 335 British Friesian bulls at AI centres progeny tested during the period 1960–65, 19% were retained for further use in the programme following selection.A time trend towards more intense selection was observed, from an initial selection rate of 1 in 3 to a final rate of 1 in 7. This appeared to involve increased culling for both daughter type and daughter production.At all stages of the programme approximately 50% of the selection practised was directed towards attributes other than milk yield.A comparison of the mean contemporary comparison (c.c.) values of the selected bulls with the values obtained following selection solely for milk yield indicated that the inclusion of daughter type as a criterion of selection reduced the c.c. value of the stud by approximately 33%.A drastic reduction in the c.c. value of the selected bulls was observed to coincide with the appearance of subsequent groups of daughters in the sire proofs.