Page 84 - Waitangi Angus 2021 Catalogue ebook

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.
CARCASE WEIGHT EBV (kg) is based on abattoir carcase records and is an indicator of the genetic differences
in carcase weight at the standard age of 750 days.
EYE MUSCLE AREA EBV (sq cm) is calculated from measurements from live animal ultrasound scans and from
abattoir carcase data, adjusted to a standard 400 kg carcase. This EBV estimates genetic differences in eye muscle area
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