Page 6 - Hauroko Valley Sale Catalogue eBook.pdf

PIKOBURN ANGUS

Understanding Estimated Breeding Values (EBVs),
Selection Indexes and Accuracy
EBVs

CALVING EASE EBVS (%) are based on calving difficulty scores, birth weights and gestation length
information. More positive EBVs are favourable and indicate easier calving.
CE % DIRECT = DIRECT CALVING EASE - The EBV for direct calving ease indicates the influence
of the sire on calving ease in purebred females calving at two years of age.
CE % DAUGHTERS = DAUGHTERS’ CALVING EASE - The EBV for daughters’ calving ease indicates
how easily that sire’s daughters will calve at two years of age.
GESTATION LENGTH EBV (days) is an estimate of the time from conception to the birth of the calf
and is based on AI and hand mating records. Lower (negative) GL EBVs indicate shorter gestation length
and therefore easier calving and increased growth after birth.
Birth Weight EBV (kg) is based on the measured birth weight of progeny, adjusted for dam age. The
lower the value, the lighter the calf at birth and the lower the likelihood of a difficult birth. This is
particularly important when selecting sires for use over heifers.
200-DAY GROWTH EBV (kg) is calculated from the weight of progeny taken between 80 and 300
days of age. Values are adjusted to 200 days and for age of dam. This EBV is the best single estimate
of an animal’s genetic merit for growth to early ages.
400-DAY WEIGHT EBV (kg) is calculated from the weight of progeny taken between 301 and 500
days of age, adjusted to 400 days and for age of dam. This EBV is the best single estimate of an animal’s
genetic merit for yearling weight.
600-DAY WEIGHT EBV (kg) is calculated from the weight of progeny taken between 501 and 900
days of age, adjusted to 600 days and for age of dam. This EBV is the best single estimate of an animal’s
genetic merit for growth beyond yearling age.
MATURE COW WEIGHT EBV (kg) is based on the cow weight when the calf is weighed for weaning,
adjusted to 5 years of age. This EBV is an estimate of the genetic difference in cow weight at 5 years
of age and is an indicator of growth at later ages and potential feed maintenance requirements of the
females in the breeding herd. Steer breeders wishing to grow animals out to a larger weight may also
use the Mature Cow Weight EBV.
MILK EBV (kg) is an estimate of an animal’s milking ability. For sires, this EBV indicates the effect of
the daughter’s milking ability, inherited from the sire, on the 200-day weights of her calves. For dams,
it indicates her milking ability.
SCROTAL SIZE EBV (cm) is calculated from the circumference of the scrotum taken between 300
and 700 days of age and adjusted to 400 days of age. This EBV is an estimate of an animal’s genetic
merit for scrotal size. There is also a small negative correlation with age of puberty in female progeny
and therefore selection for increased scrotal size will result in reduced age at calving of female progeny.
DAYS TO CALVING EBV (days) indicates the fertility of the daughters of the sire. It is the time
interval between the day when the female is first exposed to a bull in a paddock mating to the day when
she subsequently calves. A negative EBV for days to calving indicates a shorter interval from bull-in date
to calving and therefore higher fertility.
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